The battery light came on the truck last week (right before my got a little loose in it and put through a fence!). I have had the battery and alternator tested, and both test fine. The headlights don't flicker, and it cranks over just fine.

Any idea as to what can be causing the light to come on?

99 reg cab 3.0 4x4 auto no mods yet

Thanks

 

Faulty votage regulator. Mine would be at 14.1 for a good while then drop to 12.2 for 10 secs then kick back up to 14.1. The batt light would either flicker or stay on for a few minutes.

 

I'll have to check that out tonight. Thanks

Wait, is the v.r. built into the alternator?

 

Yes,its the tan looking box thingy in the back. Just get a new one or have yours rebuilt.

 

measure the voltage across your battery when running. I think it should be above 13.8 volts.

If you take it in to a auto parts shop to have it tested, they only test at one rpm. I had a Grand Am that when you got above 3k rpms, the lights would cut out and all electrical had real problems. Tested fine at the shop. Brought it home and voltage dropped when rpms went high. Shop must not have turned the alternator fast enough to produce the problem.

 

Lets add a twist to this! how about when doing down hill or when you go to pass someone and kick it down a gear. Lights dim and battery light comes on. Tested the VR and ran at 14, battery tested at 12.5.

 

Might even be as simple as cleaning your battery terminals. Sounds like the battery is holding a good charge and that the alternator is charging correctly too.

 

Def could be the battery terminals. I haven't had a chance to look at it though. Maybe this weekend.

 

SOme alts when on their last leg will drop votage when spun in higher RPMs.