Battery lights stay on

ROBERT BAILEY2

MEMBER
1991 TOYOTA CAMRY
4 CYL
2WD
AUTOMATIC
155,000 MILES

The other night the battery and brake lights came on. Took the car to AutoZone the next day, had they test my battery. They said it was a bad battery so I purchased a new one.

Coming home from work the same day, I noticed my lights were very dim, the dashlights, etc. On the freeway, I slammed on the gas but my car acceleration had slowed and slowed to a stop. I pulled over to the shoulder and turned on my hazards. Even the hazards starting slowing down as if power was draining from the car.

After Googling around, I was sure my alternator was the problem. AAA guy said the same.

Went to AutoZone got two alternators. They said, "if your VIN number begins with a 1 or a 4, get this one." Did not think my car needed anything special. It did not work. The second one I got from another AutoZone. They said, "if your VIN number begins with a 2, take this one." This time, I tell them, my VIN number begins with a J. Still, they tell me, their alternator is from Canada and the first number in my VIN number sequence is 2 so it should work, it did not.

Tried an independent alternator shop who was adamant that they had the right alternator. Installed and it did not work.

Called Toyota and they have got the special order alternator, took my VIN number, etc.

I only self-diagnosed the problem. Could it be a fuse or wire? Does this actually sound like it is the alternator?

3 Replies

CARADIODOC

MECHANIC
33,864 POSTS

Nothing you described points to the battery, although it could have easily failed the standard load test. To tell if the charging system is working, use an inexpensive digital voltmeter to measure battery voltage while the engine is running. You must find between 13.75 and 14.75 volts. If it stays near 12.6 volts or less, there are four wires on the generator to check. The large, white output wire must have full battery voltage all the time, including when the ignition switch is off.

The smaller white wire must also have full battery voltage all the time. The blue/yellow wire must have full battery voltage, but I cannot tell from the diagram if that is when the ignition switch is on or only when the engine is running.

The yellow wire is the turn-on signal from the "battery" light on the dash. If the light turns on, that circuit is okay. At the generator, you should find that yellow wire is at around 2.0 volts with the ignition switch on and the engine not running. When the engine is running and the charging system is working, the internal voltage regulator will put battery voltage back out on that yellow wire. That, along with the battery voltage on the other side of the dash light, makes the bulb turn off.

Tell me what you find on those wires with the engine off and with it running.