Charging problem - alternator/regulator

Charging problem - alternator/regulator

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tvrolet

Original Poster:

4,280 posts

283 months

Thursday 21st June 2007
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OK, not strictly an 'engines & drivetrain' topic, but as there isn't an electrical forum, here's my tale of woe.

Engine is a small block chevy with an alternator from an unknown source and a separate regulator...source similarly unknown. The wiring's real simple...in addition to the heavyweight battery feed, there's 2 wires out the back of the alternator to the regulator, an exciter and whatever-the-other-ones-called. The whatever-the-other-ones-called then 'Tees' off at the regulator tot he charge warning light. So, another way to look at it is the charge warning line runs off the whatever-the-other-ones-called wire off the alternator, from which the regulator also hangs off.

All of this worked just fine until I had to take the engine out and put it back in for a clutch problem. As far as I was concerned nothing was touched in the charging system, excepy now the charge light doesn't go out, and I can tell from a dash voltage reading it's not charging, plus the alternator spins with no load.

So, here's what the problem isn't! I've continuity between the regulator and the alternator; the regulator and alternator both have good earths; the alternator's got a good connection to the battery; the drive isn't slipping and it's spinning. I took the alternator and regulator off and took them up to an auto electician who bench tested everything (although I didn't see them actually do it) and they reckon the alternator is charging (they said a little high if anything) and the regulator's fine.

But whan I put the 'working' alternator and regulator back in the car it still doesn't charge. I called up the auto electician again who tested the alternator and they're convinced it's working fine and couldn't shine a light on why it wasn't charging in the car...except for no earth, no continuity etc., which I know is fine.

I have my suspicions that it might be the regulator, and althouh they say it tested fine I'm wondering if they just tested the alternator?

If I disconnect the charge light from the regulator then it goes out, but of I disconnect the whatever-the-other-ones-called wire (which also feeds the charge light) from the regulator but keep the charge light connected it stays on. Is this right? Or, what else can I test?

Grrrrrrrrrr.

And it all worked fine before I took the engine out....