Battery light

FABMASTER

MEMBER
1998 LEXUS ES 300
3.0L
V6
2WD
AUTOMATIC
98,000 MILES

I have replaced the alternator 3 times and replaced the alternator fuse and the battery. As soon as I replaced the battery it didn't make it more than 15 minutes and the battery light came back on. I took it to my mechanics and the tested all the wiring and the whole system. They said there was nothing wrong but the alternator was intermittent and a bad alternator. Changed it out and got green light throughout as of a day ago this morning got in and the battery light was on hence the new battery. Now 15 minutes later the light is on again. I could definitely use some help here. The alternator fuse wiring and battery are all tested and new?

Saturday, September 21st, 2019 AT 12:24 PM

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Hi,

The battery light obviously means the control module is not seeing proper charging voltage. This is between 13.2 and 14.8 volts when the engine is running.

Let's start at the beginning and find out what your alternator is actually producing. Take a volt meter and put it on the battery posts when the engine is off and tell me what you have. Then start the engine and tell me what the reading is. Obviously red lead goes to positive and black to negative and make sure it is set to volts.

If this is not within spec then we need to address that even though they are new they are below spec and causing the light to come on.

If they are within spec, we can run down a false light. This is rare on these older vehicles which makes this one a head scratcher.

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Saturday, September 21st, 2019 AT 5:28 PM