Battery light on

IIRC re the belt, I didn't pull the fan on mine Seemed easier to make the final stop for the belt on the alternator b/c it was right next door to the tensioner on mine.

 

I read most of this thread.

2007 2.7, 385k miles, original alternator. Battery is good, connections clean and tight. ScanGuage shows 14.1 volts at start, drive awhile and it drops to 13.5 volts. Then it abruptly goes to 12.5 and continues to drop to 11.6 (or so) on a routine 11 mile drive. Overnite, never fails to restart and have the same symptoms as noted but I figure one day it will stay at 11.6 and not start. I assume alternator but figured I'd run it by the experts here.

 

No expert here, but it's definitely not normal to drop below 12V. I don't think it should drop below 13V from my understanding. Sounds like an alternator but hopefully others can provide more insight.

 

99% chance its an alternator. But still check positive and negative cable connections.. at the battery and also where the neg attaches to frame and engine and where positive attaches to fuse box. Basically grab the cables and flex them around, make sure they're snug and not wiggling loose

An alternator can drop out intermittently and cause a random drop in charging voltage.. but so can a loose connection

 

Alternators will put out less voltage as they heat up or at lower RPM so it makes sense you would see a higher voltage on a cold/initial startup. Tapering down to 13.5ish is expected but the continuing to drop below 13 and 12 is not. I would confirm measurements with a multimeter but I'd agree you have an alternator going out.

 

Thanks for those tips. No loose wires. Can a dealer or auto parts store hook up some thingamajig
and confirm or do I just buy an alternator, do the swap and see if that's it?

 

Autoze used to do a load test on battery. I want to say they can test the alternatorbut it has to be off the vehicle. But its been a while since ive done that.

 

I know a battery test is supposed to be simple, but the past two times Autozone said my battery tested healthy, the battery died shortly thereafter within a week or two. Coincidence maybe.

 

I don't know for certain but I'm pretty sure the Auto parts store alternator test is very simple and will not catch all failure modes, and may have to be off the vehicle. Basically it just spins it up and checks that the output voltage is above the threshold and says its good. In your case it would likely find yours good as like you said when it first runs it's putting out enough voltage.

 

I can take my voltmeter and go for a drive, stop and check the battery across the terminals when the different numbers come up. I don't think it's the battery - why would it recharge itself to 14 volts overnite? Like I said, I'll just get a new alternator and go from there. 385k miles - it may be due.

 

Mine will occasionally hit 12.5 to 12.7 but I have to have the aftermarket stereo blasting and have my Ultragauge catch it right at the bass hit. Even at that it would never drop lower until my alternator was on the way out at about 130K.

Same 2.7 engine here..13.0 even is acceptable for our engines. I'd say get you a Toyota remanufactured and drop it in yourself, buy once cry once. Zero issues ever since.

 

All fixed. New alternator installed. Starts at 14, hits 13.5 after driving around awhile.