TheSamba.com :: View topic - Alternator light is on after I start the engine..

Thu Dec 12, 2002 2:39 am

But after I rev it the light turns off.
Is my alternator about to go?
Thanks

Thu Dec 12, 2002 10:56 am

I have seen alot of red lights(alt/gen) glow slightly and usally more at night with electrical on or like in your case when the brakes are applied.

If you check your output with a VOM and see that it is putting out (12.95 -14.25 range) with nothing on at a high enough idle for it to be "cut in",( then just for grins start turning on lights and step on brakes ect. and see wht the meter does) and are having no other charging problems then I would chalk it up to resistance in the old wiring.
As wiring gets old it can get tougher for the juice to flow through it..
i.e. resistance builds up... you could do some things like check all your grounds and clean all the terminals on the fuse box ect. ect. and see if makes it go away, but it may not be anything but a pet peeve. I 've had several models that the light glowed dimly and never had a problem for many years ( save normal battery failure every 3-4 years)

Thu Dec 12, 2002 11:05 am

Mine stays on but real dim after I start, for about a minute until I drive normally. Is this trouble?

Thu Dec 12, 2002 1:08 pm

Alternators have a "cut in speed" slightly higher than the generators. Amaze if you start you car and don't rev it up it may not go out until you rev it above 1100 RPMs
Also you don't say if you have the AL-82 with the built in regulator or the original Bosch or more likely stock Motorola alternator, both of which have a regulator under the rear seat...

79, your is the stock I am guessing, right? you problbly do not have a problem, it may be the old regualtor is slow to wake up and let the juice start flowing or it could be brushes getting worn and the commutator dirty....

Thu Dec 12, 2002 2:37 pm

keifernet, thanks for the response.
Thats exactly what it does..
My alt has a built in regulator theres nothing under my rear seat....
Also i would like to add when ever I step on the brake the alt light slightly goes on, now i'm thinking thats a short or something...
please correct me if i'm wrong..

Sat Dec 21, 2002 11:16 pm

If'n you have a Bosch alternator, this is normal. If you have a Motorola alternator, this doesn't happen.

If the charging light glows...and the faster you go the more it glows, the ground between the engine and chassis is not a good connection.

Remember, the engine and transmission are mounted in rubber...the ground strap between the transmission and chassis must be a good connection.

What's happening, is that the alternator is using the bulb in the speedometer as an additional source to ground.