Abdiel Gonzalez

Hi

I've read a bit, but as usual, I'm kinda confused now.

My '82 SC is not charging the battery. Suspected a bad ALT, I went and ran some test, but no charge at all. After reading, I learned the "BATTERY" indicator on the dash needs to be on while key is on ignition position to confirm the circuit is OK, and the Alternator charge the battery. I removed the gauge, and check the bulb which is fine, and I can get around 11.08 Volts when I turn the key to ignition, but the bulb wont turn on. Does this mean another problem, or is it the cause of the non charging? I haven't removed the ALT yet thinking on an easy fix.

Please advise!

Abdiel

r911

did you get the battery tested at a shop?

what tests did you run?

Abdiel Gonzalez

Battery is around 5 months old, or even less.

If I start the car and put the tester, I get 12.61 V when it should be above 13V.
If I turn on lights or any other thing that uses power, voltage drops exponentially. I had the battery charged overnight with a Deltran Battery Tender.
not sure what other test I can perform.

r911

take the car to an electrical shop and have them do a test of everything

where are you located?

theiceman

The bulb provides the excitation current for the alternator. This must come on when ignition is on. There is also a resistor in that circuit. There is more than enough voltage to light the bulb so double check this. Sounds like something is wrong with this circuit.

wwest

If the slip ring brushes are worn out, one of them is not making contact, the bulb will not light.

oldskewel

When my alternator failed, that charging light went out and never came on again (regardless of key position, engine running, etc.) until I replaced the alternator.

Confirming what that light should do: it should turn on when the key goes to ON (and while the engine is not yet running). Then once the alternator is providing sufficient voltage for charging, it will turn off.

If the engine is running but there is a fault in the charging system, the light should normally come on, alerting you to that problem.

But as I found, some problems can cause that light to go off and stay off at all times.

r911

don't recall exactly, but if x of the 4 diodes in the VR fail the bulb will not light at all insted of just flickering

but he needs more data on the system to diagnose what is really wrong

if the VR is internal and IIRC it is, then pull the alt. take it in and have it rebuilt at a good elc. sho - they will do the diodes, bearings, etc. and test it

then be careful putting it back in so no cables get crimped and cause a fire later on...

I like to loctite the critical fasteners for the wires - use Purple (low strength)