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'81 pickup charges at about 13.3 volts with no accessories on----with the lights or heater fan on, it dro[s to about 12.7 volts. I think I have a 55 amp. alternator and it is fairly new. I'm thinking of getting a 65 amp alternator (I don't have air conditioning), But maybe some one can suggest an alternative possibility for this issue as to cause.
 

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James, this sounds like a tired voltage regulator to me. There isn't much to fool with on them as the one I have for the Motorola alternator is sealed up and just works or it doesn't.

I have read that some regualtors can be fooled into thinking they have more load on them by addding some resistors in some manner but I can't find that bit of information right now so I can't be sure it is actually something we can do on our VW's or not.

I like to see more voltage at no load then 13.3, more like 13.8. I have a good output on my 55 amp alternator and with the lights or heater on, big draws on the system, I have over 13.

The problem with the alternators you would buy for a replacement may not be any better than what you currently have going. I would have them test it on a bench before I bought it. But then some of those test just say good on the meter face or a green light comes on. You don't really know what the actual voltage is unless you bring your own meter and have them measure it for you. If you touch the alternator you might find that you end up buying it, even if it isn't what you want. Store policy?

You have been a member long enough to know to clean your grounds and I have one that comes off the engine to the alternator so you might see if doing that or just use a jumper cable from the ground to the alternator and see if that changes any of the readings. Cleaning a ground on a VW never hurts anything and is so easy to do.
 

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Well, I would suspect a couple of things to remedy that.

If you haven't replaced your grounds from Battery to frame and frame to engine, do it. Same for the power cables.
Flakey grounds cause a variety of issues with these critters, and the fact that the OEM ground wire is unshielded allows for corrosion to build up.
So you could test for voltage drop at the grounds.

The motorola Alternator is fairly robust the weak part is the Voltage regulator. You can remove it and clean the commutators of the alternator (thing the brushes contact points, and in between them scrape the carbon off with a straight pin. A normal alternator puts out about 13.85V-14V, any more and you will boil out your battery.

You can upgrade to a Cabriolet or Euro alternator 65-90-120A outputs, and then you do away the connector on the Motorola and use Soldered Ring connectors.

I had the same alternator on my Rabbit Diesel Motorola for over 300K, but I did buy a couple of regulators over the years.
 

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Possibly the alternator belt needs tightening or replacing along with cleaning the pulley contact surfaces. On my 85 Golf, found the belt was tight when cold but loosened up when engine warmed up causing slackness.
 
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