Battery warning light on dash (charging system)

I am posting to hopefully get input on, and share my experience related to, a battery warning light on my dash. I have a 2006 4 cylinder 4WD base tacoma. One time during several months of limited use I noticed that my battery warning light was on on the dash. The next time I drove it the light was not on. The next time I drove it the light was on and it has been on every time since then. I did some testing with a multimeter based on some youtube vids I watched and while the readings were on the low end of acceptable they seemed to be acceptable and consistent. 12.4 at battery with vehicle off. 13.8 with vehicle on at battery, between alternator and battery, between battery and vehicle ground when the truck was running. Battery was 7 years old so even though I was not convinced that was the issue I replaced it. The warning light on the dash continues to come on after battery replacement. Had the following tests performed at auto parts store.


1 Autozone in car alternator test while installed in truck and truck running - said alternator was good

2 Advance Auto bench test - they ran test cycle three time - said alternator was good

3 Advance Auto bench test at a second location - said alternator was good

4 Autozone bench test - they ran test cycle three time - said alternator failed the "lamp off" test but passed 3 other aspects of the test (I think what passed was B terminal, ripple test, and lamp on)


The wires near the connector that plugs into the alternator look good (no chaffing or bare wires)


I did not get a clear explanation of the "failed" test from the guy at autozone but after some reading online I think what it means is that the alternator is operating properly but it is just not sending the correct charge to the light on the dashboard. If anyone can confirm that it would be appreciated.


I am tempted to get an alternator from a junkyard on ebay for $60 and see if that eliminates the light on the dash. Any thoughts on that? Or should I just get one with a warranty from the parts store...approx $200? Or toyota for $325? Dealer wants a flat $75 diagnosis fee in addition to whatever cost of repair would be.


Thanks for any input and I will update the post if/when I do something.

 

Someone on here had a problem that 1 of the small wires in the harness going to the alternator corroded and was not making connection. I think they unwrapped a few inches of the harness and found the problem. Don't remember all the details.

 

If you have another vehicle, take the alternator to an alternator shop to do a bench test. They can rebuild it for you too, but it may take a day, or more if they have to order parts. Alternator rebuilding is a disappearing field but they can still be found in major cities.

 

I had the battery light turn on in a corolla where the alternator totally seized up and caused the accessory belt to snap. No power anything but it started. Replaced the alternator (with another $25 junkyard Denso) and belt, then was good to go.

 

I would check the wire that goes to the lamp on your dash.

 

Check your battery voltage with the engine off. Should be around 12.3-12.8v.

Start the truck and check better voltage again. If the alt. is good it should be around 14.3v.

I had a golf that would start on cold days with the battery light on, shut the car off and start it right away no more battery light. Few months later the alt. packed it in and I had to replace it while out of town.

 

https://www.tacomaworld.com/threads/battery-light.144814/#post-18685899

 

Check it for what?

https://www.customtacos.com/tech.ol...6toyewd/06toypdf/ewd/2006/tacoma/h/em01d2.pdf

https://www.customtacos.com/tech.ol...toyewd/06toypdf/ewd/2006/tacoma/h/em01d45.pdf

 

Sounds like one of your field diodes has failed. As long as the main diodes are working, you're fine. Problem is now you won't know when one of the main diodes or VR takes a crap.

 

Follow-up. Thanks to everyone for your replies. I decided to get a remanufactured Carquest alternator from Advance Auto. A very easy DIY job on my 2006 4 cylinder. It eliminated the warning light on the dash so it looks like my problem was the alternator. I would have liked to get a Denso alternator (Rock Auto has them for a great price) but I didn't want to deal with returning the core by mail and the Denso only had a 1 year warranty.

 

Those "free alternator tests" sure turned out to be useful huh?