Just bought this truck with 233K miles and the alternator is a reman. Battery light is always on and would like some help to get it off. Here is what I have done:

1) Battery has 12.5V when engine is off and 14.4V when rnnign with A/C and lights on.
2) Took alternator to Advance and Auto Zone to have tested. Passed both places.
3) Took battery too and it tested good under load.

What else can I do?

Thanks,
Randel

 

Welcome to the site..

Alt basics..

Key in the 'ON' position, voltage is applied through the 3 wire alt connector warning indicator circuit (LG/RD wire~light green/red tracer) to the voltage regulator and the regulator is then turned ON allowing current to flow from battery sense circuit (OG/LB wire~orange/light blue tracer) to the generators field coil. When the engine starts up, the generator begins to generate current through the output circuit (B+ or large alt terminal connection). Since your seeing a charge indication, then the regulator has been turned ON.

Once the generator begins generating current, a voltage signal is taken from the generators stator and fed back into the regulator through the stator circuit (S terminal/circuit or WH/BK wire~white black tracer). The voltage feedback signal of generally about half the battery voltage is used to turn 'OFF' the battery warning indicator/lamp. If the warning lamp isn't being turned off on a startup, check for the feedback voltage on the WH/Bk wire. Being it was bench tested and seemed to pass, does the voltage still stay within upper limits on the vehicle in higher RPM ranges with no added in loads?