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Discussion Starter #1
I have a 1980 diesel rabbit, no A/C, 4 way fan. I have the Service Manual but all the wiring diagrams are for 3 way fans. Would anyone have a schematic they could scan for me? I just need the one relevant page. I have five wires going into the blower
1. black/red
2. black/yellow
3. white/red
4. white
5. black
any guess as to which one is supposed to be ground? the voltmeter wasn't helpful.
 

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Are you sure you don't have a car that originally had A/C and it was removed? The 1980 without A/C only had a 3 speed fan. If that is the case, you would need to look at the wiring for the A/C equipped car. Bentley has the wiring diagram for A/C equipped cars with four speed fans.
 

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Discussion Starter #4
yeah, I'm sure you're right now. I must have an A/C car with the A/C removed. These fans switch the blower on the ground side unlike the non-A/C cars which switch the blower on the hot side. makes a bit of a difference when you're troubleshooting.
 

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You have to have 2 things in a DC circuit, 12v+ and a ground. You say you have 12V, but you don't know if the ground is there.


Here is a picture of how that harness is tucked way up under the knee bar drivers side.







Here is a 83 cabriolet wiring diagram, it should be pretty close to what you have.







Now let me try to explain it.


At the switch pin 5 black/red a dual wire there is 12V being supplied via a fuse.


When you move the switch from position 0 to 1 the switch is going from red/black to the black/yellow wire through the entire resistor assembly (max resistance) to the fan. To place a positive voltage on the top of fan.... the current flows from the brown ground to the motor to reach the b+ being supplied at 1/4 the speed.


When you move the switch from position 0 to 2 the switch is going from red/black to the red/white wire through 2/3rds of the resistor assembly (2/3rds resistance) to the fan. To place a positive voltage on the top of fan.... the current flows from the brown ground to the motor to reach the b+ being supplied at 1/2 the speed.


When you move the switch from position 0 to 3 the switch is going from the red/black to the white wire through 1/3rd of the resistor assembly (1/3rd resistance) to the fan. To place a positive voltage on the top of fan.... the current flows from the brown ground to the motor to reach the b+ being supplied at 3/4 the speed.


When you move the switch from position 0 to 4, the switch is going from the red/black wire to the black wire which then is causing the a/c relay to pick. When the a/c relay picks 12V positive (full power) is being supplied from a different source (a/c fuse) straight from the battery to the motor no resistance, causing the motor to be at full current or as fast as it can go.


Resistors oppose current flow, the more resistance in a circuit, the slower the fan goes.


Positions 1-3 are fed from the red/black wire and fuse 14 in the above circuit.
Position 4, by-passes the switch and supplies 12v non resistored or straight juice to the motor via the a/c relay.


Now if you follow the links that I had earlier shown you, you can take the blower housing off your car, to expose the motor/resistor.
You will see that there is but 2 wires that attach to the motor, one is ground, and the other is the dual wire red/black.


If you jumper 12V+ from the battery to the red/black take off, on the motor, it should spin freely.....
If it doesn't then you are missing the ground (ie: the burnt pin I mentioned). If you then jumper ground to the brown wire, and 12V to the red/black.... the motor should spin, if it doesn't then the motor is bad.


You can also test the speeds by applying the 12V jumper to each of the different feed points of the resistor.... white, red/white, black/yellow.. The motor will spin at different speeds.
With the cover off it is a good time to use some wd-40 on the motor bearings....To clean them up...and lubricate them.... Do not spray a running motor, it has sparks, that will ignite the Butane that propels the wd-40.... (Can we say FLAME ON....)...


You can also verify that the switches are setting the voltage at the resistors...


1. Verify that you have voltage at the switch in all 4 positions. (you stated you did), so the fuses are good.
2. Verify that the ground is good going to the motor.( 5-6 pin connector on the side of the heater box.)


I suspect that either the ground is toast, or that the motor is.


It is a simple circuit.....


Now the switch harness is screwed to the heater controls at the back with a tie-wrap. It goes down and around, and it usually right above the heater floor outlet.


The White Nylon (molex) connector is supplying all the wires to the motor. It makes it easy to disconnect it to remove.


If you are going to take the Plenums off (air ducts or covers) I suggest cutting the hoses off at the fresh air intakes as the plastic feeds can be brittle with age.
Using a 12-18 inch number 2 phillips is a godsend.


On the passenger side, there are 3 screws that you get from under the passenger side knee bar. 2 hold the fresh air plenum, one holds the fan cover plus the 2 vacuum feeds.


From the drivers side knee bar there is but one phillips screw that you can see is nutted on the top cover, and then the one screw that you see from the engine bay.


Remove the housings by sliding to the passenger side of the car.


When you replace the covers use new closed cell foam. Clean around the mounting points in the rain tray,.. This will insure that you have maximum seal,,, Use closed cell, and not the really black or stryofoam looking type.
 

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Discussion Starter #6
Thanks for the detailed reply.

I'm going to try to tackle this again now.

This is an A/C model car. I have the Bentley VW Manual and while I can't seem to find my exact wiring diagram, I think that the switch actually switches to ground. Its the only one of the VW models in my bentley that switches the ground side instead of the hot side. Regardless, there's lots of good info in your reply that should help me get this sorted out. thanks.
 

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Discussion Starter #7
I disconnected the white wire connector that we've been talking about. (The one that connects wires that go to the blower to wires that go up under the dash and I guess to the blower switch) I put my ohm meter on all these five wires in every combination to see if I couldn't learn something about the state of the blower motor. every reading was continuous (0 ohms). as far as I can tell, this would be a strong piece of evidence that the blower motor itself has failed. would you agree? I suppose the next step would be to test the blower directly by removing the plastic shroud etc.
 

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No. A blower motor is a big bunch of wires that have 2 points.
It will read a short unless it is spinning.


Take the switch off the connector.
Key in and in the run position.


From ground measure the voltage on the red/black wire (should be a dual wire set, that is 2 red/black wires) should be 12V.


yes/no.


Key off.
Yes next step, no replace the fuse.


Replace the switch.
Key in the run position.
Position 0 Measure for 12V from the ground (frame) to each of the other wires out of the switch
Should be 0, save for the red/black wire.


Move the Switch to the 1st speed. Measure for 12V to ground, as it should only be on 2 of the pins. Red/black and another color...
yes/no.
Yes go to the 2nd speed and repeat. No replace the switch.


Now that we either have a bad switch..... which you have replaced, or.... we have 1 of 3 things remaining.


A bad GROUND to the Motor, A bad resistor, or a bad motor, all of them require you to remove the motor blower housing.


First test is to jumper 12V and ground to the motor from the battery... If the motor spins.... then you have a bad ground wire at the harness connector under the knee bar.


If you remove the motor covers, use a little WD-40 on the motor, and spin the blower..... it should be free to spin.... Now apply the power and see if it works. It could of been dirty, and crudded up.


On the Fresh air intake,,the one with the servo on the flapper, if yours doesn't have the screen over it, then you may want to get some window screen (nylon type) and cover that hole, as the open hole is an invite for leaves, debris, mice, and birds.
 

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Discussion Starter #9
again thanks, I will follow all of these directions. But I think that this car (1980 Air Conditioned Rabbit) actually switches the ground side of the blower motor. I looked in my Bentley's manual and while I couldn't find my exact schematic, the closest one I could find, actually switches ground and not +12V. Regardless, all of the information you've given me is valuable and can be used to regardless of whether +12V or gnd is being switched. Thanks so much for taking the time to help me with this!
 

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Discussion Starter #10
I drew my blower motor circuit the best I could for you. (see below) Here it is and also the results of some tests I did. I would like to apply +12 volts to my motor and ground it, to see if the motor itself will spin. Can you tell which of those wires coming out of the motor is ground? I'd like to see if I can get the motor to spin without out tearing into the housing. Could you tell me what the rest of the wires coming out of the motor are-- low, med, high speed.

1. Voltage measurments at point A (with the plug removed from the switch)


Y/Bk +12V
Bk +12V
Gy +12V
W +12V
Br 0V


2. Voltage measurements at point B (with white plastic connector pulled apart)


R/Bk 0V
Br/R 0V
Y/Bk +12V
Gy 0V
W 0V


3. When I wiggle the wires behind the fuse panel, the +12V readings fall to 0V


4. I am not sure if the wires marry up the way that I depicted them in the diagram. For example, the Gy wire at point B probably doesn't connect to the Bk wire at point C. I got a little lazy and didn't take good notes on that.
 

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Nope, it switches +12V... There are only a couple of circuits where VW switches the grounds they are the door switches for the courtesy lights, and the Radiator fans in the early rabbits the cold start valve thermal time switch, parking brake oil pressure and coolant temp, fuel level, and the seat belt. Otherwise it is the Positive side that is being switched...


It all works the same.


e=ir (Ohms Law) you can't get around it.


The issue is that your motor isn't spinning, and you think it isn't getting the voltage, which it could be, but from your earlier statements I am betting that the Ground or the fan itself is bad.


Oh, the fan is a high priced item.. I know I had to buy one once. I then got a couple out of a wrecking yard as they were only 10 bucks. I rebuilt them.
 

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I think if I recall correctly, now that I think of it, mercy sakes probably is in fact correct that ground is being switched.
The 1980 model is a little bit funny compared to the later years. I don't know why I didn't think of it earlier since I am in the middle of an air conditioning transplant from one car to the other.
I will post a diagram later this evening that may help, not right now though got to take care of something outside yet. So stay tuned.....
 

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Does this look like your wiring setup? This is for a 1980 rabbit diesel with A/C, but should be the same on gasoline models:


This is the motor and resistor that is used in this system:


and the fan switch wiring harness:
 

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Discussion Starter #15
This is my wiring diagram that I made myself from looking at the actual wires in my car and yes it resembles the "switches at the ground side" diagram that lobster head posted. The colors of the wires just before the heater fan are Bk/R, W/R, Bk/Y, Bk, and W. Can anyone tell me which wire is ground out of those? Which is hot for the highest speed of the fan? I should mention that in my diagram, I didn't take the time to see which wire meets which wire at each junction and my ohm meter couldn't answer that question for me. Blower Motor Circuit.jpg
 

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Well if that diagram is similar to what you have, then none of the wires are ground, since ground is through the switch. The red/black wire should be hot whenever G7 on the fuse panel is hot (it is connected to ignition/starter terminal X) and your fan switch is in any position other than off. That is because that is the conditions necessary to energize the A/C relay. You should be able to read positive 12+ volts on the red/black wire with a meter to ground under these conditions.
 

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Discussion Starter #17
Right that makes sense. Let me ask you this, though. I want to jump 12V and ground from my battery to the wire block coming out of the fan. The block with wires Bk/R, W/R, Bk/Y, Bk, and W. So am i correct that I should apply the HOT to Bk/R and that I can pick any other wire for GROUND. I am trying to see if I can get my fan to turn. Muchas gracias.
 

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If all you want to do to see if your fan will spin, yes you can apply positive voltage to the red/black wire and ground any of the following which will run the fan at different speeds: Black, White, Grey, Yellow/Black. That is your four different speeds. Part of your problem I think is that the colors actually change after the connector. The wires directly out of your motor are not the same as what is on the connector that the motor wires plug into. If that is the case, it is probably a replacement motor. You will have to look at the connector that your motor plug connects to. Those wires should match the diagram.

Unrelated - Just for added strangeness, the 1980 non A/C equipped three speed diagram does switch positive similar to the 83 Cabby diagram posted above.
 

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Right that makes sense. Let me ask you this, though. I want to jump 12V and ground from my battery to the wire block coming out of the fan. The block with wires Bk/R, W/R, Bk/Y, Bk, and W. So am i correct that I should apply the HOT to Bk/R and that I can pick any other wire for GROUND. I am trying to see if I can get my fan to turn. Muchas gracias.

No... The Bk/R, W/R, Bk/Y, Bk, and W are feeds to the resistor they aren't grounds. You can apply 12V to those and the motor should spin, if you apply ground you will blow the fuses, and possibly burn wires.....


VW uses BROWN for grounds, if it ain't brown, don't ground.
 

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I think he meant with the blower motor disconnected at the plug:

He can put 12V on the red/black wire and then ground one of the other wires and the motor should spin. When the motor is plugged to the harness, the Bk, W, GY, and Y/BK are +12V until the fan switch is turned on, then the circuit is completed to the brown ground wire coming directly off the speed switch.
 
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