No alt light

[Tac]

It has happened to most of us. Working on one thing and something else happens. I did a search for No alternator light in different forms and all I been getting for results are "my alternator light is on. Just the opposite. When I put the key in the ignition and turn it to the on position the alternator light is doesn't go on. I have about 13 volts in the battery. and everything seems to be ok. Anybody know what's going on?

Tom

[url=http:www.mediafire.com/convkey/7340/e29fqva0ooqus716g.jpg[/img]http:www.mediafire.com/convkey/7340/e29fqva0ooqus716g.jpg[/img[/url]

[82vdub]

There's a feedback wire that runs from the alt (at least on 86 vintage) that runs the alt light. This wire could have a short, a bad connection, or the LED light could be burned out. If you have a Bentley, there should be the wire that runs from the alt back to the dash for this light shown in the wiring diagram.

[TylerDurden]

The blue wire on the alternator frequently gets broken inside the insulation, right near the alternator. Engine vibration is amplified out there away from the crank's center of rotation.

A good test is to meter the battery before starting the engine, and again after revving... the voltage should go up.

If the voltage does not go up, a jumper of +12V to the exciter terminal of the alternator should make it go up (engine running).

With the key off, there should be no voltage at the small terminal on the alternator. Key on, there should be ~11V until the alternator kicks on and then there should be the same voltage as the output of the alternator.

[wmasscaddy]

Also check the 5 amp fuse labeled "radio". It powers the whole dash cluster. If it's blown the battery won't charge, but it might take a while to notice.

[Fatmobile]

I think the regulator can cause this too.
Remove it clean the ground spots and reinstall.

[Tac]

Thanks that's a lot of good info. That's this week ends project, after I fix my heat situation.

Thanks again
Tom

[Tac]

You guys were right. It was the exciter wire. The blade connector was broken. After I repaired it, It still wasn't on. After tracing the wire I seen it was broke at the plug near the battery. I just touched it a little bit and the red wire broke right off (age and heat I guess). Light is working the way it should. Got another problem with another dash light I'll post in a new tread.

Thanks again, pics below for any one having the same problem.

Tom

https://www.mediafire.com/folder/phq1sn ... aba/shared