New alternator and alt light stays on

Hmmmmmmm. You're saying that the light comes On even with the Key OFF??

If so, I would have to assume that there is leakage current in the diodes inside the alternator. (Look at the Motorola alternator diagram on my web site.)

If you have a voltmeter, connect the meter from ground to D+ on the alternator. Key OFF. Wire disconnected from D+. You should read zero, or close to zero. If you read near 12V, I think the Alt has a problem.

Speedy Jim

There shouldn't be any voltage even getting to the alternator if the key is off, should there ?

Randy

Yes, there is always voltage on the big B+ terminal from the battery. The internal diodes are *supposed* to block this voltage from going "backward" into the alternator. Jim

But why would there always be voltage ? Wouldn't that just run down the battery ? I'm getting confused as usual.

Randy

When the diodes are good, they won't let the current through. Hence, no drain. The B+ goes directly to the battery positive terminal.

Jan

No, it's pretty straightforward. The fat wire goes to B+ on the Alt. The Blue wire (under the back seat) goes to D+ on the Alt. You have to use one of the existing regulator wires to extend Blue into the engine bay (the skinny Red wire is the logical choice).

There's alternator wiring info on my web site. Speedy Jim

Well shit. I guess I already knew that. Another senior moment. It's hell getting old.

Randy

Or, as Kate Hepburn said "Getting old ain't for sissies."

Max

But much better than the alternative.

Mike.

Thanks for the info. Your website is very interesting. Electricity has always been a huge mystery for me. It looks like my alternator is bad. I also noticed the shaft (where the pully nut screws on) is magnetized. Does that mean anything useful?

Ted

I doubt it. Jim