Generator 101

[Thing7]

Can someone school me on my generator? I'm trying to find out if my charging system is working correctly. I've read through some previous posts but I wanted to make sure I'm clear on this.
I don't drive at night much but recently when I did, I noticed the "G" light on my dash was on. I believe at idle it wasn't on, but while driving it was on. Which could explain my next discovery. I tested for voltage with positive post on left and negative on right "see pic". At idle I was getting 11-12 volts and when I throttled up it went down to like 3v. First off, am I checking the voltage properly? I also think I read that if you disconnect the positive battery terminal and the engine dies within a couple seconds, that the charging system isn't working properly. Is this true? Because I tried that and the engine died. BTW...new battery

So if I'm properly checking the charging system and it's not charging, what's my next step? Does anyone have a write up on how to check and replace generator brushes and anything else that would need replacing?

Thanks

[hazetguy]

first off: take one of those plastic brush covers off. you are going to cook the bearings and/or generator if you have two of them on.
secondly: the generator is oriented 90 degrees off to the left. this also affects cooling. it's somewhat easy to fix this: remove fan belt, loosen generator strap, remove the 4 bolts that hold the backing plate to the fan, rotate assembly to the right (clockwise), reinstall bolts, tighten clamp, install/adjust fan belt.

regarding charging: check the brushes to see if they are tall enough and making contact with the armature. they should be sticking out of the top of the brush holder. that's the first place to start (after removing one of those brush covers).
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[Thing7]

Thanks hazetguy...I'll start checking off those things and see what I discover

[heimlich]

There's a good writeup here: http://www.vw-resource.com/generator.html
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[Thing7]

Hey folks...So I've done a lot of trouble shooting this weekend to see why my system isn't charging.

I've tested the battery while at idle 12.9v. Revving engine doesn't change so it's not getting a charge to battery.

I've tested voltage directly from generator by disconnecting D+ and Df, grounding Df and checking for voltage at D+ with engine at idle. Result at idle is about 22v. As I slowly increase throttle the voltage goes up to about 39-40 BUT as soon as the idle increases any further the voltage goes whacky and doesn't read anything that makes sense. What would cause loss of voltage as the generator spins faster?

[Thing7]

[Wildthings]

[Thing7]

Yes I have checked the brushes but I didn’t know what you just told me about the top of the brush being even withholder could mean they are toast. I pushed down on them with generator spinning to see if things changed but it didn’t. Maybe it’s time to replace

[Thing7]

Well I had a new generator and regulator installed last fall and I assume it was charging because the generator light on dash was not on. The Thing was in the garage for the winter and I pulled it out a couple weeks ago. The generator light was on at idle (can't remember if this was the case after the new generator was installed) but as soon as I would rev the engine the light would go out. I drove a few times and it seemed that I had to give more rpms to get the generator light to go out. It got to the point where I would have to really hit the gas hard from idle or tach it out in first or second gear in order to get the generator light to go out. Then after driving around town the light would not go out no matter how hard I revved the engine. I have done all the trouble shooting. The generator is putting out around 30-40 volts. I even put a new regulator on. I've check all the wires between the generator and regulator. I'm at a loss.

[BJT]

I’ve had my Thing for a little over two years. Granted a rarely drive it at night, but when the headlights are on, the generator light flickers on. Has always been this way, and I replaced my brushing earlier this year, which resulted in no change. My guess is it’s probably just old wiring/connections and a 40+ year old generator just doesn’t work like it did when new.