Battery light stays on - checked everything - Page 2 - Toyota 4Runner Forum

Bluesky 07 · 07-15-2022, 10:02 PM

Quote:

Originally Posted by greasefingers

When the battery light comes on it does not indicate that the battery is bad but tells you the charging system is not supplying enough power to the battery.
With the engine running at 2000rpm and no accessories on, the voltage at the battery should read about 13.9 to 15volts. Toyota does not specify and plus or minus range:-( which everything has. Your reading is 13.93v so the alt is great. Forget about the dashboard icon being lit. Here in VA one can not fail a vehicle inspection for a battery light lit.

I just replaced my battery and alternator and wondered why the battery light never came on. This might be the answer. Seems the voltage regulator may have been the issue since voltage was swinging randomly between high 12’s & low 15’s so while the alternator needed replacement, enough current was flowing to keep the battery off. Does that logic track?

IBallEngineer · 07-15-2022, 10:15 PM

Quote:

Originally Posted by Rsbhunter

I posted about the same condition. I replaced battery with a new one, 12.7 on batt, replaced alternator, 14.1-14.2 after starting , 13.7-14.0 idling. Checked every fuse, engine bay and dash....all good. Starts fine, runs fine, just was on after sitting for a week. Where are the ground wires? I know about the one on the fender by batt. Any others? Sorry to hijack thread, but this is maddening... rsbhunter

The Battery light is supposed to come on when you turn the key on because the Gauge fuse is sending power to the light and it is grounded in the voltage regulator inside the alternator. When the engine starts and the Alternator is charging, the voltage regulator sends output voltage back to the light, which turns off the light since it no longer has ground. if you could back probe the gray wire on the alternator plug, you should see alternator voltage when it is running, if not, the internal voltage regulator is bad. Which in essence means replacing the alternator unless you are crazy, like me.

AuSeeker · 07-16-2022, 08:40 AM

Quote:

Originally Posted by IBallEngineer

The Battery light is supposed to come on when you turn the key on because the Gauge fuse is sending power to the light and it is grounded in the voltage regulator inside the alternator. When the engine starts and the Alternator is charging, the voltage regulator sends output voltage back to the light, which turns off the light since it no longer has ground. if you could back probe the gray wire on the alternator plug, you should see alternator voltage when it is running, if not, the internal voltage regulator is bad. Which in essence means replacing the alternator unless you are crazy, like me.

If he is crazy like you what would he do instead of replacing the alternator?

IBallEngineer · 07-16-2022, 05:05 PM

Quote:

Originally Posted by AuSeeker

If he is crazy like you what would he do instead of replacing the alternator?

R&I the alternator, pull it apart and replace the bad regulator. Or install some oversized overamped unnecessary high performance alternator. Or pull the motor and install an LS, just sayin'. Good thing even I come to my senses most of the time.

achord24 · 09-11-2022, 03:14 PM

Any luck on solving this issue? My light stays on too. I just got back from a 1000 miles trip. Light on prop 80% of the drive. Obviously not a prob, but I hate seeing that!!!

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