I'm at my wits end, I have a 2010 Toyota Corolla 1.8L 4 cylinder with 140,000 miles on it. Recently the battery light has been coming on intermittently and the voltage on the alternator drops down to around 9 volts and isn't charging the battery. It also only seems seems happen when the car is already warm as the alternator puts out the full 14 volts when started cold and only dropping after. I've already replaced the alternator twice already and the problem still comes up. The connector for the alternator was loose but even after cleaning it and pushing it in all the way it still gives low voltage. And when the lights on the sensor for the lights doesn't work and I have to turn on the headlights myself. Far as I can tell no fuses have blown either. I've already put a ton of money into this car fixing a bunch of other problems and I'm ready to tear my hair out.
Intermittent problems are the worst. It can be very frustrating to find the cause when you can't reproduce the problem.
Be creative and do your best to trigger it. Try things like:
- driving over bumps
- turning on various combinations of electrical accessories
- turning A/C on a off.
- wait for the radiator cooling fans to turn on
- turning the steering all the way left and right (electric power steering)
- wiggling your wiring harnesses around (under the hood, in the door jamb etc.)
- look for other symptoms that happen at the same time.
- you can also touch all your fuses with a finger to see if they're getting hot
etc.
The only symptom I've noticed besides the battery not charging is the headlights and dash lights not turning on at night like normal. I've turned on all electronics in the car when the light is on but it still runs, just too low to charge
"still runs, just too low to charge"
well that's the event you need to trigger to further troubleshoot your issue ... the battery light and low voltage.
Once you can reproduce it reliably, you can start pulling fuses to isolate the circuit.
you should also inspect/clean your grounds, like the strap from the engine block to the body. Might as well give all the cables a once-over while you're at it.
Besides what Joe suggested, do you know about the history of the car?
Nope, sadly don't know the history of the car. I don't believe it's ever been in a wreck as most of the parts are factory originals (besides the ones I've replaced)
There has to be some high resistance in one of the circuits somewhere.
or it's a short (low resistance) path which is pulling down the voltage.
Correct - also could be a bad voltage regulator in the alternator, if it's internal type.
unlikely since he's on his 3rd alternator, but if the voltage is computer controlled then that could be another avenue of failure.
Good thought. Maybe all three alternators were assembled on a Friday afternoon? HA!
can't rule it out. They could all be cheap reman alts
True, true.
Not that it’s too reassuring but has the concern gone away at all even if briefly after each alternator? I have done (especially when using aftermarket) repeat alternator replacements. One car I had to do 3 before finally getting a good one. Otherwise I would make sure your pin fitment is tight if the connector is coming loose
