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disqo 04-03-2010 08:59 PM

Battery Light On?
I returned home after a week away and at the end of my hour and a half drive from the airport something strange happened when I shut off my car. The battery light on the instrument cluster stayed on. It was still on with the car shut completely off and the key removed from the ignition. The headlights are off and I even removed the faceplate on my stereo to see if it made a difference. The only thing that made the light go out was disconnecting the negative lead to the battery. I tried restarting the car with the idea that something different might happen when I shut it off. When I turned the key to the glow position the glow indicator light did not come on. The car started easily, but it is warm outside and the engine was already warm. The pertinent info seems to be: No glow indicator and battery light stays on after I turn off the car no matter what. When the car is running the light is not on. I have never heard of anyone having this problem before. Any ideas?



aaa 04-03-2010 10:04 PM

Check the voltage, on and off. Mine turned on a week before my battery died.

pwjeep 04-03-2010 10:35 PM

Could also be your voltage regulator... which doesn't charge your battery enough. Voltage regulator is on the back of the alternator with 2 screws. It can be changed without taking the alternator off the car, but it's kind of a pain that way. You need a stubby screw driver and smaller hands. Check the voltage output of the alternator when it's running at the battery... it should be 14+.

disqo 04-03-2010 11:58 PM

Thanks for the responses. I have changed the voltage regulator before and I am pretty sure that is not it. When the voltage regulator went bad, the battery light was on with the car running. Mine only comes on when I shut the car off. It is on with the car off, the ignition off, and no key in the ignition.

layback40 04-04-2010 02:35 AM

There are only 2 ways that the light would stay on with the ignition off

1/ power is connected to the thin wire at the back of the alt via the reg.
2/ there is power still connected to the down stream side of the ignition switch.

Disconnect the thin wire at the back of the alt reg. Put a volt meter on the wire, if 0volts then most likely reg problem. Put volt meter on tab on reg. If a few volts (dont need 12) then reg is faulty. If 0 then the problem is some place else, maybe the loom.
If when you test the wire you get voltage, then ig switch is bad or loom fault.

charmalu 04-04-2010 03:28 AM

Check the ground strap from the body to the engine.

I had the battery light stay on with the key removed. before that, I had the temp gauge bounce around, and some time seem normal, then peg all the way to the top.

this had me pulling my hair out trying to get to the bottom of it.

I checked the ground strap, and it was tight. but later decided to remove it just to see if there was some corrosion under it.

I had replaced the engine with a new rebuilt. well it had been painted, and that kept it from getting a good ground. scraped off the paint and everything is back to normal.
funny thing is, the engine was in the car 2 yrs before this developed.

I knew it was a ground, just didn`t know where.

disqo 04-04-2010 10:50 AM

I appreciate you guys keeping the advice coming. When I turn the ignition to the glow setting the light does not come on, but the relay does click and the car starts as usual. I checked the small wire that runs to the back of the alternator and there is no power coming from it. What tab would would I check on the back of the alternator to see if the problem is the regulator?


layback40 04-04-2010 11:12 AM

did you disconnect the wire first? You unplug it with the thick wires, then you can test to see if you have a voltage on the wire.
You then test the pin that it would have been connected to.
The other lead from the volt meter needs a good earth.
One of them should have a voltage if the light is to be on when the plug is in the back of the alt and the motor is not going.

disqo 04-04-2010 11:19 AM

When I disconnect the plug, the light does go out. I tested the small wire itself on the plug. I will go back out and test the pins that come off the back of the alt. My plug has two thicker red wires and a smaller blue wire.


layback40 04-04-2010 11:24 AM

Shane, the blue wire goes directly to the light. If the pin on the alt it plugs onto is live when the other 2 thick wires are connected, then the light will glow when the ignition is off. This would suggest a problem with the alt/reg.

If there is power on the blue wire with the ignition off, & its disconnected from the alt, then you have a problem with the ignition having power when its off.

Be careful the 2 thick wires will be live (12 V), The turbo makes it hard to get at the back of the alt !!

I hope that is not too confusing. :)

layback40 04-04-2010 11:35 AM

Your post 8 makes me think the problem is the reg or the alt. If the problem was in the ignition circuit you would have had power on the blue wire when it was disconnected. I assume you are using a digital volt meter.

disqo 04-04-2010 11:44 AM

I am using a digital volt meter. There is also no power reading from the pin that corresponds to the blue wire on the back of the alt. I had to move the car and with the harness unplugged from the back of the alt. the glow light worked as normal, but the battery indicator light on the dash was not on while the car was running. I would think this light should be on while the car was running if the harness was unplugged.

layback40 04-04-2010 11:50 AM

No the light wont come on with the harness not plugged in to the back of the alt. That tells me that the ignition wiring is ok and the prob is the alt/reg

disqo 04-04-2010 12:01 PM

What do you think the next step would be? Should I replace the voltage regulator again as a stab in the dark? When I talk about the voltage regulator I am talking about the spring loaded thing that goes into the back of the alt. I hope this is correct.

JimmyL 04-04-2010 01:35 PM


Originally Posted by disqo (Post 2441075)
What do you think the next step would be? Should I replace the voltage regulator again as a stab in the dark? When I talk about the voltage regulator I am talking about the spring loaded thing that goes into the back of the alt. I hope this is correct.

Yes and yes, and doing that first is a lot easier than replacing the alternator.
Our friend down under has really given you good info in this thread! :)

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