Hello, I need some help.

I already searched and I went ahead and bought a voltmeter and tried to diagnose the parasitic drain. I attached the meter across the negative cable with a 1 ohm 10w resistor. I attached the meter across the resistor and pulled all the fuses in the engine compartment and the interior compartment. I saw no significant in drop. My readings were .30 mv. A draw from the battery did shoot up to .77 mv when the door was open and I pulled fuses from the inside of the car. But I attribute that to the door being open and there was no change.

As of late, when I go and drive the car after it has been sitting over night, the battery light will stay on until about 5 miles into the drive. But after messing with everything yesterday and going out to dinner, the battery light will go on and off while driving. The car starts up just fine but I think it’s because it has a new battery.

Please help, I really don't like the ideal of disconnecting the battery every time I drive my car.

 

Is the Car bone stock?

Did you install a headunit?

Was it a flooded car?

Aftermarket alarm?

Red?

Blue?

More info.

 

Sounds like a alternator issue. I would check the connections and stuff for it. You can also go to autozone or a place like it, and they can perform a charging system check on it for free. A small power loss like what your describing * as in small* would not make the battery light come on while driving for sure.

 

The car is stock ,125k. I bought it from an older man who had records since 99. Stock radio, no alarm (stock alarm,) I don’t think it was flooded and it is blue. The previous owner did tell me about the parasitic drain and he installed a negative battery quick disconnect. He hardly drove the car so I dismissed his prognoses as not driving the car enough. Previous owner took it to a shop, and the shop could not find the problem.

I thought it was the alternator as well. I did take it to AutoZone yesterday and had them run a test. Everything checked out.

This morning I drove it to breakfast and the light stayed on. After breakfast I was going to go back to AutoZone to have them run the alternator test again. But the battery light did not come on.

 

The previous owner last fix for this problem was 1/6/10. The car was taken to lexus of glendale. they installed a new battery to resolve the drain and had a new ecu transmitter fix for the remote entry. He had a new battery installed 1/28/12.

Okay, made it to autozone w/ the battery light still on. They put there tester on, reading said voltage regulator failed. battery light did go off on the way home. So does this mean the alternator is going to fail soon?

 

The voltage regulator can either be seperate or on the alternator itself. Most newer cars and I would imagine are lexus's have voltage regulators on the alternator itself built in. Have someone confirm this. Then replace the alternator if it does have a internal regulator.

 

I just read that the voltage regulator can be replaced. Bolt on item. Anyway hopefully thats the cause of the drain. thanks for the responses everyone. Ill update after i get it fix.

 

Its not a drain, its that its not letting the alternator charge the battery. Which explains the light. Glad its something simple and not a electrical grimlen.

 

Regulator is internal.

Also there is a 12v+ switched on the alternator harness, to tell the ALT it's ok to recharge the battery.

After I did my bare bones swap, I kept killing batteries cause I didn't have the ALT 12v+ connected.

Some places will even rebuild yours for like $60, which is good, cause you keep the OEM housings.