The alternator on my 78 didn't seem to be charging. I checked at the alternator and was only seeing battery voltage ( 11.5v at this point). The alternator was not charging. I removed the alternator which looked brand new and took it to my local AutoZone to have them test it. Lo and behold it checked out as GOOD. WTF? I think my wiring may be wrong at the alternator. Here is a pic to explain what I mean. If anyone can chime in as to whether I need additional wires or not I would appreciate it.

 

No takers?

Bump

 

I'm not sure about the early alternators, but I believe you are missing a ground on that third connector (the regulator). The large wires are power, the small wire is to the charge indicator light. I believe the third one is the regulator and goes to ground. How did they hook it up when testing? Also, I think if the charge indicator light is burned out, it will not charge.

 

Hook up the ground connection - test what voltage you get on the small terminal when the Ignition is On - it should not be 0V if it is Bill could be right about the indicator buib or the wiring to it or the resistor (if you have one).

Alan

 

Ah, good, the A- Team has arrived!

 

So it grounds through the spade terminal? At the AutoZone they grounded the case with an aligator clip. By the way, the spade terminal that had nothing hooked to it has a large W cast into the case right next to it. I'll try grounding that terminal and see what happens.

Thanks

 

That's not the alternator the car came with, it looks more like the mid-80's Audi 5000 alternator that is frequently used as a cheaper replacement. I wouldn't worry about the spade terminal -- Mine worked fine without that(until it didn't -- overheated due to no cooling shroud IMHO).

Anyway, does the alternator/charge light on the dash work? Try grounding the small wire that had been attached to the alternator -- with the key on and this wire grounded, the dash light should come on. If it doesn't, you need to replace the bulb or figure out what's wrong with the wiring. There may be a 68Ω 5W resistor in parallel with that bulb, mounted to the back of the cluster. '78 cars did not come with that resistor, but there is a tech bulletin stating it should be replaced when installing later alternators. Don't leave this wire grounded too long(>30 sec) while testing, since if you have the resistor it will get pretty hot.

Here's the alternator I pulled out of my car -- as you can see it looks very similar to yours: