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?

Thanks

Shane

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

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+.

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.

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.

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.

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?
Thanks,

Shane

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.

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.
Thanks,

Shane

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. :)

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.

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.
Thanks

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

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.
Thanks

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! :)

I would first pull the reg out (2 screws ) replace the plug in the alt & see if the light is on. If its not then chances are the reg is bad. if its on then reg may be good & alt is bad.
I once had an insect get in the back of the alt, it got fried & then the alt light just glowed dim all the time.

How does your post #5 determine if the alt or the reg is bad? Or are we just to replace both & keep our fingers crossed?

If there was a problem with power getting to the ignition side of the switch (loom problem) and the alt/reg were good, the light would go out as you described.

Given that the OP said that he had replaced the reg some time ago, I am left wondering why 2 regs may go bad. Is there some other problem?

If the alt is bad, it may be the second set of diodes (exciter diodes) that are the problem. There may be some foreign object lodged in the alt doing it.

It may not be as simple as we may want it to be. I have seen plenty of so called "bad " alt's that people have paid a lot of money to replace, with very little, if anything wrong with them. Too many just start replacing stuff until the problem goes away!! Pars suppliers love that approach.

Maybe we all need to "Look Listen & Learn" !!!!!

Well,
I tried replacing the voltage regulator today with no success or change in the problem. It looks like I am on my way to a new alternator unless anyone else has any ideas. I really do appreciate all of the help. I do need new belts anyway.
Thanks

Maybe the last reg replacement was just hiding a alt on the way out?

A new alt/reg is the next step.

Your old reg maybe ok but I dont think you want to take the risk.

Make sure you get a new one or a good quality re-manufactured one. I think it is worth inquiring on this site, Fastlane Phil has been very competitive in the past.

You could also look at an upgrade to a higher amperage alt.

Good Luck!!

Some folks just need the affirmation of "credit due".... :rolleyes:

Best let high balls go through to the keeper !! :D

Straight From Bosch
 

I picked up a remanufactured Bosch alternator today and rather than going through all of the effort of installing it first, I just plugged it in to the harness and surprise, the light on the dash did not come on. The problem indeed seems to be a bad alternator. The new alternator came with a little manual and right in it is says "Alternator warning lamp comes on with the ignition switch turned off: If this situation occurs, there is a bad diode in the alternator...remove and replace the alternator." Man, I wish I had seen that about two days ago. I am going to replace the alternator tomorrow night and do all new belts at the same time. Anyone have any special tips about the belts or alt? I am about to search the archives to see what others before me have had to say. I appreciate all of the help and I hope this thread can help others with the same problem.
Thanks!