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A layman 's Guide to electrical diagnosis and repair

First you need a few tools:
Diagonal Cutters
Wire Strippers
Soldering iron Butane is cool
Rosin core solder (Multi-core is good)
Electrical Tape
Heat Shrink tubing
Amp Pliers
Various AMP (solderless) connectors
Wire of Various Gauges
1 Digital VOM (Multi Meter) Voltage/Ohms/Current
1 12v test light
1 Noid Light bi-directional non polarized digital tester
Rubber gloves
Sand paper
Wire brush

First things first
Voltage is Felt at the terminal or connector
Current Flows across the terminal or connector in the circuit which isn 't to say that if you become a current path between the battery and ground you don 't feel the current.

Basic rule of thumb is Ohms Law
E (voltage) = I (current in amps) X R (resistance measured in ohms)

For every change in current with voltage remaining constant then resistance has to move up or down accordingly. That is why when a fuse blows you have current increasing that causes the fuse to melt and since the 12v battery is constant the resistance had to have decreased (shorted).

There are 3 types of normal conditions:

Normal, that is that every this is acting correctly.

Open, that is that part of the circuit is open to current flow and caused the circuit to stop working. (as in a connector that popped off).

Short, that is that part of the circuit is causing a direct path to either 12v plus or ground.
Ground to ground shorts is okay, a 12v to ground short is a bad thing.

Current in a circuit flows from Negative to the Positive source that is why you will find most fuses are tied at the source.

Fuses are bi-metallic devices that are rated for the current that they safely can carry, they can never exceed the rated value, when they are called on to exceed the rated value they usually crap themselves and open up. These are to protect you from wiring fires, electrical shocks, and lastly destroying valuable components.

Connectors, on autos corrode naturally because of a couple of factors salt air, water, or dissimilar metal corrosion also called Electrolysis, that is where you mix 2 base metals and pass current between them.

Battery Cables are not only subject to electrolysis but hydrogen sulfide (Acid) from the battery and that is why you have to clean them regularly.

In a car almost everything save for the alternator is 12vdc or direct current rated, current that flows in one direction only.

The Alternator produces Current and Voltage in alternating current or AC hence the name alternator. This is current that changes from positive to negative and back.
The designers add a voltage regulator to change the ac of the alternator to dc using a bridge rectifier circuit, and a current limiter Alternators are easier to regulate and produce a more constant and fluid current and voltage, than a DC generator.

Relays and solenoids are devices designed to be operated by lower current devices and switch on or off High current loads. Ie: headlight relays and starter solenoids.

Relays usually are for 30 amps current circuits or less and solenoids are for the higher drawing circuits like starters.

However all relays have small solenoids in them usually or a solid state device that acts like a solenoid. That is why you hear the click when one is energized it is moving a physical itty bitty switch.

In electronics there are only three types of devices, resistors, capacitors, and inductors. Every kind of device acts as one of these three things. Oh they may say that they are solid state but they actually are a type of resistor.

Practical experience tells you that if you short a positive source to ground there will be Sparks that can ignite volatile fluids or objects.

What do I do with a VOM?

You can take specific measures of Voltage ac/dc, resistance, or current.

To know how to measure we have to discuss the two types of circuits in use, and they are series and parallel.

Series circuit is a circuit that has a source of voltage and devices in a straight line from the ground to the positive source.

Parallel circuits have multiple paths from ground thru devices to a positive source.
Most circuits in a car are in parallel. That is why one fuse controls a variety of things.

There are rules that are not bendable in circuits as current flow in a series circuit is constant, only voltage and resistance will vary. Whereas in a parallel circuit voltage is constant and resistance and current will vary.

Since most of us aren 't worried about the current in a car specifically, in circuits except for knowing the charging circuits are producing enough amperage to keep the battery charged, we usually rely on fuses to tell us if a circuit is over current.

Knowing that the diameter of the wire expressed in gauge (12ga) determines the amount of current that the wire can carry. A small diameter of wire carries small current. If you try to carry large current through small wire, it will over conduct and the conduction causes heat which melts the insulation that causes fire or sparks when the bare wire touches the chassis and hopefully shorts to ground blowing the fuse and keeps you safe.

Large current devices have big honking wires (starters, alternators, motors.)

To measure voltage you place the negative lead on ground, and touch the positive lead to the point of measure, you should always see 12vdc or very close to that. If you measure a light bulb when it is energized you will find 12vdc positive on one side and 0 on the other respectively.

If you are measuring a circuit and see 11.5 or 10vdc you are looking at something that is resisting the voltage, this is one reason we tell you to clean all connectors. Some devices can use reduce voltages to function like a light bulb that glows dimmer, but some solid state devices will not function with the reduced voltage. The average solid state component will not energize with as little as a.25Vdc difference. Clean connections ensure that proper current and voltage are applied to the circuit.

A fuse that looks good may not be good, you really have to test it. That is if you place your black probe on ground, with the key switch on, you should see 12Vdc on both sides (the little metal tangs at the top) on a fuse. You can also take the fuse out, and putting your meter on resistance (lowest setting) see it read 0 ohms or that the fuse is shorted and functional.

A fuse is either shorted (normal) or open (blown up).

A 12VDC test light is another good way to test for voltage and current, you clip one side to ground, and then prick things to see if you have a good high light or a dim light.

I know that I have been saying 12Vdc and if you measure a battery directly you can have anywhere between 12, and 13.5 volts as normal. The difference is how the battery is made, the number of cells and the material that each cell is comprised of determines the true voltage of the battery so if you are reading 13.5 volts at the battery to ground that is the normal voltage for you. When you turn the car on and you see it drop or increase significantly then you have either a bad alternator that is producing too much voltage or one that is not producing enough. I have placed a new alternator on a car, and as soon as I started it all the light bulbs started glowing really bright, I measured the voltage at the battery and it was 18Vdc which told me that my new alternator was bad
Too much will blow out all the light bulbs prematurely, and possible explode the battery.

Always have them test it at the store before you leave, that way you won 't have to remove the new one to take it back to get another good one like I did 5 times once.

What does a switch do, well they are used as a low current device that turns on or off a circuit, they also can be used to turn on or off a relay that can in turn, turns on or off a solenoid.

Relays and Solenoids are used to shunt current loads, so that you don 't have to run large gauge wires to the dash and back to energize things.

A relay that is close to the object that you are trying to switch on or off will carry more current without loss to the device. This is why when you install a headlight relay close to the battery and the lights and uses it to switch the lights on and off; works better and your lights are brighter.

This is why the HOT fix for an automatic tranny starter involves wiring a relay to shunt the power directly to the starter solenoid So that the starter can get maximum current at start.

Next installmant: Connecting a to, and what to use when.

Now this is a general what it is reference, not specific to anything in general. Car 's and electrical problems go hand in hand, on older cars it is a given.

If you have specific questions on reading a schematic (fancy term for wiring diagram) I will try to answer them. The Chilton 's book breaks the basic diagram out from the standard Bentley, but because of the parallelism of the VW schematics, you have to look at the whole current path when diagnosing a problem, this is what leads to proceeding down the wrong path most times, or missing the problem point because you can 't see what the cigarette lighter has to do with the instrument
lights enjoy

Which connector should I use, and why?

I am only an average Joe schmuck, and I want to use a solderless connector, because I am so bad at soldering.

Solderless connectors are fine for most work; they are also referred to as AMP or Crimp connectors, and are a product of the AMP connector company originally.

They come in different shapes and sizes and color coded so that you can match the color of the connector to the gauge of wire that should be used with it. They are a quick and effective method of connecting two wires, or adding a spade or female end to the wire.

They have their limitations and here they are.
They are not waterproof and are prone to weakening the wire by the improper application of the crimp, which can nick the wires or cut them internally. They are also prone to vibration.

You don €™t want to use one on a critical circuit that vibrates all the time unless you solder it after crimping.

I have seen them become loose and the wire back out and cause some damage like burnt wires, arc welding to the block, and blowing a fuse or two.

To properly use them you have to match the connector to the size or gauge of wire, you can €™t put a big honking wire into a too small connector my trimming the wire. Wires should not go past the crimp onto the terminal end, and conversely you don €™t want to have a too small of wire in a big honking connection. Wires are not supposed to out strand the connector.

To properly use a Crimp you have to strip the wire from the ferrule beginning to the end, there has to be enough insulation to cover the un-ferruled plastic portion of the connector.

Using the proper tool to crimp the ferrule correctly is a must to ensure proper closure of the ferrule to the wire (AMP TOOL).

The normal Amp tool is multi-faceted; it has a wire stripper for various sizes of wire, and a crimper on the end that is color coded for the gauge of connector that you are using and possibly a screw cutter for small screws of various widths and thread size. They are also referred to as CHAMPs, from a company that made them as in a Cresent Wrench.

First you have to select the proper connector for the gauge of wire.

Using the stripper of the AMP tool you have to use the proper size for the internal gauge of the wire.

Place the wire in half of the tool cutout and close the upper to the bottom, then twist the tool 360 degrees, then holding the wire on the inside pull the tool off to the end of the wire. You will only be using about ¼ inch of the bare wire in the solderless connector.

Twist the wire tight in the direction of the twist, usually clockwise to the run of the wire.

Insert the wire in to the Solderless connector, and using the end of the tool, place the wire and the connector in the jaws and pinch then together one quarter away from the middle of the connector ferrule.

Lightly pull on the wire, if it backs out you will need to re-crimp the wire on a new connector.

Then wrap the spliced wire with electrical tape, if it is an external wire that is subject to water I use Friction tape as the tar like qualities help to ensure a dry waterless connection at all times. Never pull to break the tape, cut it. A smooth end will adhere better and look nicer.

When splicing multiple wires stagger the splices as they will tape up thinner and look professional. Think of it as a braid, the flatter the braid the nicer it looks and the stronger it is.

If the splice is unsupported then you may want to incorporate a strain relief to it, that could be a wire tie, or a piece of twine so that the strain of the wire pulling is on the wire and not the connector.

How do you solder?

Soldering is an art, there is no kidding to it, and there are simple steps that you have to follow to get a good and fast (tight) connection. With practice there is no doubt that the connections that are soldered are permanent and have the best electrical integrity.

Solder is a precise mixture of alloys usually 60/40 tin to lead, now they are using white metal because of the EPA wienies, but in my opinion the 60/40 tin lead is far superior if you can find the 60/40 TL buy it. You will not get drain bramage from sniffing the fumes, unless you do it day in and out for a couple of years if the area is well vented then that is even better. I love the smell of rosin/solder as it is making a connection, but I don €™t snort it, you shouldn €™t either.

In the inner diameter of the solder is a rosin core, it is that rosin that cleans the area prior to the solder hitting the work area making it conducive to proper solder flow and quicker soldering. The Higher the percentage of tin/lead ratio will make for easier or harder soldering the 60/40 is best for general electrical work around the home.

What do you need?

A good soldering iron, I personally use a butane powered variable adjustable tool by Weller. Although the portable or corded electric ones are just as good.

You need a medium and a small grade of rosin core solder (acid core is for radiators and such). I use multi-core solder that is available from Radio Shack.

Heat shrink tubing of various sizes

Sand paper, wire brushes, and or files

A damp rag.

A De-Soldering tool (solder sucker) the spring loaded push button are the best

Cigarette Lighter

Various clamps as in hemostats or other locking pliers make holding hot items a breeze.

Step one Turn on the iron, and place in a non-melting holder, I use the cheap bake-o-lite ash trays that have the cigar holder in the middle, always place the iron tip up this will insure that the heat that the iron is producing goes right to the tip. If you are using a electric iron, make sure that the tip is screwed in fully, when you are done remove the tip when slightly warm.

As the iron is getting hot, you can strip and prep the wire, for an inline splice use the Western Union wrap that is where you place one bare wire over the other in a twisting fashion, clips the bitter ends of the wire to make flush 3 overhand wraps

After stripping and twisting the wire tight, place a piece of heat shrink over one half of the wire well out of the way of the connection that you are making.

Next make the Western Union splice.

Pick up the soldering iron, and wipe with the damp cloth, this will clean the tip, now touch a small amount of solder to the iron on the flat edge of the tip or the point it depends on which tip you have. This little bead will greatly enhance the transfer of heat to the wire, and reduce the amount of time the iron has to be in contact with the wire.

Make sure that your connection is taught; now with the soldering iron at the bottom of the splice apply solder to the top of the wire in the middle, solder by nature will seek the heat, Solder will start to flow when it does slightly move the iron and the solder over the wire to cover the whole joint. Do not move the joint until it is cool, doing so will get you a cold soldered joint that is where the joint looks dull and the wire splice moves as two separate wires. You don €™t need a gigantic glob of solder to make a good connection, which is actually counter productive. Solder should always be 180 degrees from the iron.

A good solder connection uses just enough solder to get the job done and no more. You will also be able to see the individual strands of wire covered with solder. If you get a big glob put the damp rag under the connection then heat it again to get the solder to liquefy, then flick the connection and remove the heat, the glob which is about 300 degrees will fall away from the wire, and into the rag.

Then quickly wipe the tip on the rag to re-clean it.

Now let it cool a minute you can blow on it to make it cool quicker.

When the connection is cool to the touch slide the heat shrink tubing back over the bare connection, and using a cigarette lighter that is lit, run it over the length of the tube and on all 4 sides, it will slightly contract (becoming shorter) but shrink to the diameter of the wire, and add strength to the connection as well as insulating it, move the flame do not let it sit too long in one area as it will ignite the heat shrink.

A connection that is soldered correctly will shine, as you are soldering with the proper amount of heat you will see the solder flow into the wire and through the connection it will look like you have silver plated the wire. If it is Dull and grey then you either did not have wire that was cleaned nor had too little heat for too little time. You don €™t have to worry about cleaning the burnt rosin off, this isn €™t the space or aerospace industry.

Too much heat will melt the insulation, the melting insulation will possibly drip and burn you or your carpet, It is not the end of the world, it just don €™t look pretty, if the insulation is all fried and crispy, as long as the joint is good shinny and solid don €™t sweat the little cosmetic crap, unless you are Lucky, but then remember that you can cover it with tape or heat shrink €¦

What is tinning?

Tinning is all about prepping the work and getting it clean and ready to be soldered and will reduce the time to make the connection.

If you are attaching a wire to a pre-existing connection you will need to clean it, you can use a degreaser like carb cleaner or brake cleaner, wipe it clean with a rag or use sand paper, files or a wire brush, you have to have it clean to make a connection.

First strip your wire twist it tight, and then apply heat from the iron and solder to it to make it shinny and clean let it cool wow you have just tinned the wire.

Now on the cleaned connector, apply heat from the iron to it till the original solder starts to melt away, add new solder on top then holding the wire with pliers on the insulation attach it to the connector keeping the heat on till it fuses together, it has to look shinny not dull. Let it cool then pull on the wire to see if it made a good connection or a cold connection the cold will allow the wire to pull away €¦.If it does just reheat and add some more solder.

Most of the terminal ends that you buy that are bare metal are zinc over copper plated brass connectors. Some times they have to be smoothed or filed flat, then with the soldering iron at the bottom of the piece apply a thin coating of solder to the top, this is where the ashtray comes in handy. You can place the iron in the ashtray pointing up, then using a pair of pliers hold the connector to the tip and apply solder with the other hand. This is actually tinning the piece €¦.. This simple little step is a time and heat saver.


Strip a length of wire about 2 inches, then twist it tight, and tin it, so that the solder has flowed through the diameter of the wire let it cool. Now using a pair of needle nosed pliers bend a hook in it, the wire will stay together and now trim it and you have just made a connection that can be screwed down, and you didn €™t have to buy a connector.

You can also take the wire and wrap it around a screw remove the screw and tin it, and it is a very tight screw connection.

Practice makes perfect, you have to practice soldering to get good at it, once you are good at making splices and hooks we will move on to other soldering and de-soldering things €¦.

You have to keep the tip of your iron clean, frequent cleaning with a damp rag helps to increase the convection of the heat from the iron to the work. Big honking wires take a lot of heat, smaller wires take little, and solid state devices are the easiest damaged by excessive heat.

Circuit Boards

Ooooooohhhhhhhhh don €™t want to be messing with no circuit boards. Some times you have to, do to age, and vibration connections on a circuit board crack loose. To repair them you have to remember that here excessive heat is your enemy, a properly heated iron, and a good solder is essential.

First turn the work over so that all of the components are away from you and you see their little legs sticking through the board. Look at the board, is it coated with a corrosion prohibitor or lacquered over? if it looks extremely shinny then you probably need to clean it off of the stuff, use 100 percent rubbing alcohol and a tooth brush to remove the crap off. Once it is dry wipe it with a alcohol damp rag.

Now holding your soldering iron in one hand you are going to do a two count to the leg of each component.

Place the soldering iron against the leg count to one, then apply solder between the leg and the iron, count two and remove. You have just remade the connection, you will see that the solder around the leg will melt if you time it right you add the solder at the moment of melting, you are waltzing with the soldering iron a one, and a two and a shuffle to the next, and you didn €™t know that you could dance.

To attach a wire to an existing hole in the board strip the wire and tin it, then feed it in the hole, then from the back add heat and solder just long enough to get it to flow then remove and cool quickly by blowing. Too much heat is your enemy too little and it will be a cold joint, timing is everything.

To remove a wire or a component you have to be quick and accurate.

To remove a resistor or a capacitor or any other device is tricky, and you can do it a couple of ways.

From the front side (component ) place a small screwdriver under one side and while you are heating the back side you can pry it out. Heat is your enemy.

You can also use a solder sucker, **** the sucker and with the iron in one hand and the sucker in the other apply heat to the component when you see the solder starting to melt place the tip of the sucker next to it and press the button. The vacuum created buy the plunger it will draw the liquid solder up in to the tool, the solder sucker tips melt so do not directly place the tip of the sucker on the iron, okay? There will be a well defined hole devoid of solder and the component will wiggle if the component is slightly attached just touch the iron to it for a second and move it about with a small screwdriver.

For any solid state component you have to use the de-soldering tool usually. When I was first starting out, there were unprotected suckers, the plunger would smack you right in the eye, and it wasn €™t unusual to see a TECHIE with a black eye. I wont be talking about solder wick, so don €™t ask.

Warnings and considerations

Soldering irons are hot, they melt stuff when you least expect it or want it be careful at all times of your surroundings.

Solder when it is hot burns.

Don €™t touch a freshly soldered connection it €™s hot and can burn you.

Big Honking Wires will retain heat and can cold solder as it cools, you have to hold the wire in a firm grip with a pair of pliers until it is cool. Spraying water on it is not the way to cool it, blowing air is.

No matter how hard you try you can not solder on mylar or the flexible circuit on an instrument cluster you will just melt it and make things worse. They make special glues to do that, ie: a rear window defroster repair kit.

Taking too much time to solder or de-solder a component on a circuit board will cause you to break the bond between the board and the circuit trace, and the trace will lift away from the board. HEAT IS YOUR ENEMY €¦ €¦ now you know why.

You can reattach a pulled trace to the board with super glue then solder. If you break a trace you can clean both sides of the break and tin them, then solder a bridge wire between them.

You have to insulate all soldered wires either with heat shrink or electrical tape.

Always remember that heat shrink works best when you put it on prior to soldering the wire.

If an existing connection is corroded with green tarnish you have to clean it before you re-solder it.

A Good Soldered connection is a permanent thing, it will ensure proper current flow for years, any time I do anything inside of a dash, I solder. Why, because as much of a pain in the ass it is to get apart, I don €™t want to have to remake a flakey connection.

I do not use the 3m Scotch-Lok connectors they loosen over time I solder.

Keeping connectors clean is a good thing, you can use wire brushes, sand paper files screwdriver to remove tarnish and corrosion from a connector. Using a pair of pliers you can tighten a female connector to make it grip tighter, go easy tho.

Di-electric grease reduces the ability of water and corrosion to get in to a connector. It ranks right up there with the Thermos bottle, it insulates when it needs to and conducts when it needs to, how does it know €¦ one of the great mysteries of electronics, the other is how can they pack so much and fire and smoke in to that little bitty wire.

This is general Car Soldering techniques; household wires require other methods for code.

Next up
What the hell are these things and what do they do?
What are all these squiggly lines?

When you are reading schematics there are symbols and things that look like they were drawn by some dudes that were smoking refer. In reality I think that they were as when you are talking about Electronics and you are deep into it you are in another world. The history of the men that formed the basic principles and discoveries are really fascinating reading.

Gallenium Silicon, strata, emitters, base, collectors, windings, current, voltage leading current, uni-junction, propagation, array 's, are all terms that are familiar to some and out of the world to others. Welcome to my world, most all Techies that I have meet who like me were or are currently designers of circuitry revolve in our own little world we look at a circuit see the symbols and convert it to a jumble of mathematic equations. Electronics is Math, Physics and Chemistry in its truest sense. There are rules that were laid down for a hundred years by brilliant men and these rules govern every thing that a circuit can do. And you wonder why you can 't make heads or tails out of it? Most of the original work developing circuitry was by folks like me with Slide rules and pocket protectors, there weren 't calculators, and computers that fit on your desk took up buildings.

One of the first mass produced computers didn 't go to a bank or credit-card company, you found them in bars, yes that is correct one of the first mass produced computers were simply a PIN-BALL machine. Ever looked inside a vintage 50 's unit? Relay-Relay logic, switches inductors all kinds of neat crap, don 't think it 's a computer, well for a given input (the ball) it adds subtracts divides and multiplies depending on the input (how many bumpers the ball hits and when). So see your Greaser father in the love of a PIN-BALL machine was the first true Gamer.

Well enough about the history lesson lets get down to it.

There are basic fundamental rules that are laid out and I will re-iterate them for you, they are written in stone, and if you accept that then you will have a fun time

Voltage expressed as E voltage is felt on a circuit path.
Current expressed as I amps flows through a circuit.
Resistance expressed as R in ohms opposes both current and voltage
Power expressed as P in Watts is equal to Current times Voltage

E=IR there are variations to it as n E/I=R

Let 's take a light bulb that is rated at 100 watts running at 110vAC
since we know that P=IE we can figure out the current of the bulb
100/110 =.9090909 Amps of current.

Now that we know the amperage of the bulb let 's find the resistance?
E=IR so E/I=R basic substitution
110/.9090909=121ohms of resistance. In actuality the bulb is a Inductor, and that the impedance is really the true measure of the resistance value, but you can get the general Idea.

Ohms laws are the founding principle and you can't get away from it.
Everything in a circuit acts as a Resistor in the simplest form.

LED 's, Transistors, relays, switches, capacitors, motors, and all solid state components in a circuit act as variable resistors.

I am not going to expand on this any more, if you want to know more there are volumes of material available on the WEB or from your library that will tell you everything that you want to know or more take it as a given.

Basic 's

The introduction in the Bentley is wrong, they tell you that current in a circuit flows from the positive to the negative, that is the way it was taught in the 50 's, and early 60 's, now that science had accurate ways of measuring the flow of holes between electron, they discovered that in fact current flows from the negative to the positive.

When you are reading a schematic (fancy term for wiring diagram), you have to remember the orientation of the page.

Rule number 1. All pages orient so that ground paths are at the bottom and supply voltage is at the top

Rule number 2. Current flows in a circuit from the ground path back to the supply path.

Rule number 3. All switches are usually shown in the off position, unless otherwise denoted.

Rule number 4. The bigger the wire or resistor the more current it can take, the more current that it takes means that they can get hot and burn your ass if you touch them.

Rule number 5. All tie points in a circuit are denoted by a blacked dot at the cross point, if it doesn 't have a darkened dot then it is not a part of the circuit that you are tracing.

Rule number 6. A failed component will cause an interruption of current flow from the ground path to the source.

Rule number 7. Fuses go, and a visual check is not the answer, you have to test it by resistance checking or by voltage testing. Yes you can usually see a 30 amp fuse that is blown, but the.5amp ones are very hard to see.

Rule number 8. Replace the fusefirst before going on.

Rule number 9. NEVER OVER FUSE A will find the problem child, but you can burn up half the wire in the car doing it.

Rule number 10. If you are measuring the voltage at a solid state component, and you see 12Vdc on one side and 11.5 on the other, all that means is that the circuit is probably working, as it takes but a small change in voltage to turn on a solid state component. Don 't be fooled.lord know I have from time to time.

A circuit that has a.5amp fuse can KILL YOU if you become a ground path.

Direct Current will stop your heart, cause you burns, and can generally ruin your day. Be careful the Average Battery in a car has 600 amps of stored energy waiting to sneak up and smite thee in thy arse. I wear latex gloves when playing with electricity.

Series circuits are designed so that a break in any of the components stops the whole show think of a string of Christmas Lights.

Parallel circuits are designed so that a given component can fail but others continue to function as needed think Light Bulbs in your house.

Expanding on Rule number 6, if a component fails, it can fail two ways Opening, or Shorting. If the fuse is good you can back track it to see where the ground path is lost by seeing where the voltage is present by jumpering it to ground with a 12volt test light to ground. This is a handy little bit on knowledge that I am imparting to you. Once you have found where the light stops in the circuit by dividing it up in bits you have found your failed component.

If the Fuse has failed and you replace it and the fuse blows again you have a circuit that is shorted from the Source directly to ground. You have to start disconnecting things to find the failed component, it is simple to do, knowing the path that the current has to take allows you to measure resistance to find the trouble spot.

When reading a Bentley or a Haynes, the engineers at VW who drew them out originally graciously labeled all the components and color coded the wires so that is a big help to the average reader, as the original VW mechanic has little if any electronic training we will expand on them a bit as needed. From reading the previous pages you probably know more than most of them already. You don 't want to know about how airplanes wiring are all the same color white, but they are numbered..

Wiring paths can change colors; from red/green tracer (little green line in the solid red wire) to a white/blue (solid white wire with blue tracer) the second color always denotes the tracer. You have to be cognizant of the wire colors at all times as you may start tracing the wrong path. Wherever the color changes there has to be a connector. This is one reason that most companies including the Armed forces will not hire you for certain jobs if you are color blind..

Reading a wiring diagram is a lot like a topography map, or a travel map, you have to zero in on the route that you are following to get from a point to your destination.

I will start by referring to a page in the Bentley, and I will give you the same page number from the Haynes Rabbit book, this way every one can follow along no matter which book you own, the books are:

Bentley Publishers
œVolkswagen Cabriolet, Scirocco Service Manual 1985-1993 �

Haynes Publications - 96016
œVW Rabbit Golf, Jetta, Scirocco, Pick-up 1975-1992 All gasoline engine models �

Are we READY? Got your Haynes or Bentley out? Lets all start by turning to page,
Bentley Main Wiring Diagram Cabriolet 1985-1986 page 4 of 5
Haynes chapter 12 Chassis Electrical Systems 12-90

We will be talking about the Windshield Wiper Circuit so that is on the left hand side of the Bentley

The years are not the same but the circuit is, and that is what counts for this discussion

On the page we see a lot of information let 's start by orientating the page 's information.

At the Top of the page we see all the source paths for 12Vdc. we can see the fuses that are in the circuit and the intermittent wiper relay. All those lines are on the fuse panel neat.

The middle of the page contains the Wires that are running through out the car from the fuse panel to the various components.

The bottom of the page has all the ground paths for us, cool isn 't it.

Lets Look closer at the books, do you see the difference if you have both open to the same pages?

The Bentleys are photocopied from the source and were never cleaned up, the Haynes are a sharper copy that they took the time to clean up. Who copied whom? The Haynes has a typo the backup light switch isn 't in the water temp gauge path? Nifty, so for sake of reading the Haynes is a little cleaner, but the Bentley ties the pages together.

When you are reading a diagram, you have to think that you are in the circuit traveling through it in the most logical path to get the source, with that being said we have to start at the ground path and work are way up the page to the source.

At the extreme bottom of the page we see that there are little numbers those are the ground path number also the current track it is also a reference number that may take you do a different part of the circuitry to another page. If you go to the index, for the main page on the Bentley and look up the windshield wiper motor, it will tell you that it is in the current track of 105-106, quickly you can follow the numbers on the bottom of the page and when it gets to 105-106 look up and you will see the windshield wiper motor.. but is doesn 't have a path to ground, so why did they say that it is at current path 105-106.because they are using the current paths as an INDEX so that you can locate things quickly.

The top of the pages have the source paths for us those are common bus points that follow from page to page

The index page of the Bentley for the Main wiring diagram tells us where stuff is located in the Diagrams, tells us where to look for things, as different Grounding point and where various connectors are located in the dash on the firewall all kinds of neat stuff s there . The Haynes book is a little devoid of that information, but they list the things covered at the bottom of the page.

Every relay that is on the fuse panel is always shown at the top of the page in the source path bus 's.

So let 's see what it is telling us first that the ground is on current track 16 and if you follow that all the way back to the origin you will find that it is in a tapped wire loom in the dash.

So looking at the circuit we start at 108 and come up the page in a brown wire to pin 31 on the column of the Steering wheel where the switch is located, from there it stops, why because the switch is in the off position doh

Let look at what all the pins of the switch are doing at rest/off then on Low then high
We have to build a truth table to help us all that means is that we need to know what the pins are doing at every selection.

Motor pins
OFF Pin 53 and 53a have no voltage
Pin 53b has 12VDC

Low speed Pin 53, 53a, 53b all have 12VDC

High Speed Pin 53 has nothing
Pin 53a and 53b have 12v

Steering Column Wiper Switch

Off 53 and 53e are mated

Low speed 53 and 53a are mated

High Speed 53a and 53b are mated and 53a 53 are mated

Intermittent 53a and J are mated and 53e and 53 are mated

Washer 53a and T are mated

Now if you are wondering what the switch is on the Motor that is the parking switch that returns the motor to the stopped (rest) position if the blades are up when you turn off the switch, as long as it is running there is nothing that the switch really does.

So we have our truth table.

At the bottom of the motor, we have pin 31 that is actually the ground path for the motor, and when we operate the switch he are providing 12VDC to the motor through the pins 53 and 53a and 53b to make it spin fast or slow or intermittent.

With the switch in the first on or slow setting 12VDC is supplied from the fuse at S11 it goes down the page to pin 53a of the motor parking switch.

12VDC is also supplied from the fuse at f11 down the page to the tie point.
Then to the left to the tie point from there it goes up the page to setup the 12VDC on the pick side of the intermittent relay and then down the page to pin53a of the switch. since pin 53 sets up the 12VDC to the bus at the switch, there is now 12VDC on pin 53 which goes up the page and to the right and through the normally closed section of the intermittent relay, but also sets 12VDC at the bias point of the solid state device backing though the normally closed portion of the intermittent relay we go down the page then to the left then down the page to pin 53 on the motor, turning on the motor. As the motor is spinning about it opens and closes the switch at 53a and 53e of the motor.

Wow all that just to get the Motor turning.

Now we are going to move the Switch to the High speed side.

With the switch in the first on or high setting 12VDC is supplied from the fuse at S11 it goes down the page to pin 53a of the motor parking switch.

12VDC is also supplied from the fuse at f11 down the page to the tie point.
Then to the left to the tie point from there it goes up the page to setup the 12VDC on the pick side of the intermittent relay and then down the page to pin53a of the switch. since pin 53 sets up the 12VDC to the bus at the switch, there is now 12VDC on pin 53b and 53 here is where it gets a little sticky.


Pin 53 which goes up the page and to the right and through the normally closed section of the intermittent relay, but also sets 12VDC at the bias point of the solid state device backing though the normally closed portion of the intermittent relay we go down the page then to the left then down the page to pin 53 on the motor, turning on the motor.
And now 12VDC is supplied to pine 53b that goes up the page to the left then down the page to pin 53b adding an additional current path to the motor.

Since the motor has two separate sets of brushes and windings and that the total current available to the motor is set by the fuse @ no more than 15Amps we have just kicked the motor into high gear. The more windings that the Motor has the faster it can spin, on low speed it is using one set of windings now with the switch on high we throw in a new set of windings. Since the motor is now getting voltage and current at 90 degrees difference instead of 180, it starts to spin faster.

Now when we turn the motor off and if the blades are not at rest, the parking switch which is normally open is now closed and we know that pine 53 and 53e are mated there will be 12VDC available to the motor until the parking switch moves from pin 53a and 53e on the motor, once that happens the motor will stop and the blades will be parked.

Now when you place the lever in the down position, intermittent you start to engage the intermittent relay. Think of it as a having a little person inside of it that is counting to two and throwing the switch from on to off.

Basically it goes like this. take a breath.

We know that there will be 12VDC at pin53a pin 53 and 53e and now there is 12VDC at 53J

So the normal low speed part still works and is there spinning the motor, but a timer circuit starts to activate (a 555 timer is actually the chip and a capacitor). Because pin 53e is at ground from pin 31 of the motor the minute that you press the switch down you charge a capacitor in the relay. (This actually happens every time you turn the switch on.) Since the motor is starting to spin the motor park switch closes to pin 53a an 53e are together once the motor get fully up, then down, the timer is starting to count a one and a two, that energizes the relay providing power to the motor to sweep for a two count up, and down wait 2 then up and down. Wait The charging of the circuit some times gets a little off, corrosion of the contacts, a sticky relay, a timer circuit that didn 't get fully charged is why sometimes the count is off or the motor stops mid way.

The windshield washer circuit basically does the exact same as the intermittent but there is a longer count to hold the motor on. The counter doesn 't start until you release the switch.

There are a lot more things that I left a little froggy here because of the nature of electronics.
Why does a motor spin? Windings? 4 instead of two

But basically you can now read a simple current path and know how to set a truth table

Hope you enjoyed

Which way should I bias a diode if I want to change my bulbs over to LED 's? And what the hell does MCD mean when I am buying them.

Series and Parallel Circuits

You have heard me say series and parallel circuits, and gone what the hell is he talking about, well since Drew, asked about wiring a "fog" light to a switch, I figured that nows as good a time as any to tell you what the differences are:

Today we will be talking about the difference between Series and Parallel circuits, what they are and how do they function.

There are two types of circuits in electronics that are common the series and the parallel circuit.

Series circuits are that all components are arranged in a straight path, the failure of one component will cause all components to fail in the circuit.These are simple to make and

In the drawing below we see that the current path when the switch is closedgoes up the page to the light bulb, then it goes through the light bulb and out the other side up to the next light bulbs bottom leg, out the other side to one side of the switch.With the switch in the open position, current can not flow it is similar to a water faucet handle, until you turn it on, you don’t get any water.

If you close the circuit now the current or ground that is on the one side of the switch can go through the switch, the little electrons are so excited that they move faster than the blink of an eye.. Current goes through the switch to the bottom of the fuse and then through the fuse to the Positive side of the battery.

Now when a component fails as in lamp one we see it has the same effect on the circuit that opening the switch has, lamp2 has no source of 12VDC to flow to, so it won’t turn on.

Now lets take a look as the same circuit in parallel below:

First let 's notice how each lamp isn’t cascaded to the next in a row, they both have separate grounds and they both have separate paths to the switch, when closed they both go back to the 12VDC positive side of the battery..

When we close the switch, current flows up from the ground to the first leg of both lamps, then out the top of the lamp through the switch and then through the fuse and can now reach the positive side of the battery.

If we take out lamp1 then close the switch the current can still flow through lamp2 and lamp2 remains lit.(Typical headlight circuit) If one lamp goes then the other remains lit, the only common point of failure in the circuit is the Switch and good old Mr. Fuse.

When you are wiring a Switch in the circuit normal Single Pull switches are in series to the current flow so that you interrupt the flow. this is why some switches have but 2 terminals on them.

There are switches that can operate two separate circuits at different times and these typically have 3 legs, the center common for the 12Vdc source and one other leg each for the separate things that it will be turning on or off.

Now you have the Basic differences between a series and a parallel circuit.

Which way should I bias a diode if I want to change my bulbs over to LED’s? And what the hell does MCD mean when I am buying them.

What are Light Emitting Diodes?

They are a product of Electronics, Chemistry and Physics, The first LED’s and such cost a lot of money to develop, but now thanks to everybody using them they have replaced
Neon tubes and incandescent lamps in most common used circuits, why you ask?

By nature the little filament in a light bulb is very fragile, they can’t take the stress and strain of the repeated on and off, AC light bulbs are more susceptible to burning out because the filaments have to take a current change of direction 60 times a second as in 60 Hertz.

Hertz is the cycles per second that a frequency is measured at. Most common house circuits are 60Hz. It is close to the beats that your average heart is going and why it is a little unfriendly to you. Radar operates at Gigahertz 1 Billion cycles per second.

A DC lamp only has to take the strain of going on, or off, the current flows in one direction only that is why DC light bulbs tend to out last the normal AC bulbs about 37 times longer.

In Thomas Edison’s house in Florida it is said that the bulbs in all the fixtures are still the original bulbs that he invented. That is because he was a big backer of Direct Current and the war between him and Westinghouse to have the main power of most cities in either DC or AC is legendary. It is exciting reading, and involves traveling sideshows of each side electrocuting dogs and cats and things. Westinghouse won the war by act of a judge giving a death sentence to a convict; this is why we have AC in our homes. Edison isn’t the only person Westinghouse screwed Tesla who invented AC was royally screwed by him. It is fascinating reading about the war between Edison and Westinghouse and the life of Tesla is really out of this world.

Light bulbs are rated in Lumens, but marketed in watts, as that is the amount of power they are using. But interestingly DC bulbs as in headlights or fog lights are rated in candle power or candela. LED’s are rated in Milli Candela or MCD for short.

So now we know that MCD is the power rating of the LED’s it is not a true indication of the power of the item, but it is as close as we are going to get. The Epoxy coating of the unit determines the actual brilliance.

LED’s use current passing over 3 different strata of materials, that current allows the electrons of the different strata to interact and produce light from their interaction.
They also produce heat, and a super bright LED can melt plastic.

LED’s use different materials to produce different colors of light like infa-red, blue, white, yellow, or red. Most colored LED’s that you see that are yellow, purple, or red are the coating of the epoxy and used to sort them at manufacture. It isn’t the true color of the LED. They are also sold by the size of the epoxy coating 1mm 2mm 3mm or 5mm are the most common sizes.

Coloring the epoxy can also reduce the amount of light that it emits.

Because of the way that they are made an LED can last up to 100,000 hours of use, the average household bulb lasts but 700 hours.

Now that we know what they are and that the rating isn’t indicative of the brilliance then a hard rule is for the instrument lamp replacement I usually use LED’s that are at least 10,000 MCD, and I think that the 5mm fit really well in the average socket.

LED’s have two legs usually one longer than the other, the shorter of the two legs tells us the polarization of the unit.

LED’s are directional I the circuit, this means that one side is connected to the most negative part of the circuit and the other is the most positive.

Also the shorter leg is on the flat side of the LED’s base.

So now we know a little bit more.

If you take an LED and attach the long leg to the positive side of a battery and the short leg of the battery you will see nothing happen, that is because it needs a different biasing and that you just probably blew it up. It happened so fast that you probably didn’t even see it.

So LED’s have to be biased, to function, that means that one of the two legs need to have a resistor tied to it. I normally use either 460 or 680 ohm 1/8 watt resistors as they can be made to fit rather nicely in the standard light bulb socket.

To Bias the LED you can attach the resistor to either leg, I always use the negative (short) leg so that the current is always somewhat limited, and they tend to last a really really long time.

Changing a Bulb out for an LED made simple

Fire up or plug in your soldering iron.

Take you average bulb, in the holder

Push in the little clips on the side so that they release the bulb from the holder one on each side.

Gently pull the socket assembly out of the holder.

Clip the holders off the bulb as close to the metal tab that you can

Trim the back side of the holder so that you can see a hole in the back, you will be pushing the legs of the led assembly through them a little later.

Replace the metal sockets back into the holder and make sure they catch.

Solder the bias resistor to the negative lead of the diode as close to the base as you can and trim off the excess leg

Now push the legs of the bulb through the holes in the back of the socket that you made so that they stick out and can be bent onto the metal tabs on the side of the holder. Push them flat onto the metal piece.

Now solder the legs to the metal tabs on the bulb.

Trim off the excess.

Now using your VOM (Cheap assed that I bought from BIG LOTS for 5 bucks) notice that it has a diode checker. Place the switch to the diode checker, and attach the leads to the spring point of the bulbs, the led should light if you do it right. If it doesn’t place the leads on the other side (diodes are polarity wise). Mark the negative side, so that you will know.

Then remove the bulb from the instrument panel and measure the connection for 12v and gnd. When you read 12vdc then you know which way to orient the bulb.
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