What Causes Battery Light to Come On

[JusTheUsual]

My old battery would barely hold a charge. So the past week I been driving around and no battery light until the other day. I finally bought a nice 1000ca battery and the battery light is still on. I have a newish alternator 130amps instead of the stock 90 and my battery gage finally goes just above middle position with new battery and alternator. But why is my battery li9ght still on when it just came on other day with older battery and got new battery today? What causes the battery light to come on?

 

[drdoom]

I believe it is for malfunction of charging system. What is your actual reading with multimeter?

 

[Flash]

The light does 2 things.

1. It provides a load to excite the field windings so that the the alternator will charge. Once the alternator is charging 2. the light will go out letting you know that the alternator is working.

Your alternator isn't working.

First thing - check the drive belt and tensioner.

 

[koda2000]

The light does 2 things.

1. It provides a load to excite the field windings so that the the alternator will charge. Once the alternator is charging 2. the light will go out letting you know that the alternator is working.

Your alternator isn't working.

First thing - check the drive belt and tensioner.

Or. it may be working, but the charge isn't making it back to your battery. Check the alt wiring and the mega fuse at the back of the power distribution box. If you have a VOM, check the voltage at the large terminal ("B") on the back of the alternator. If less than 13.5-14.6 volts the alternator isn't charging. Most likely your alternator is not working, but you should check the other stuff it might be before you lay out $120-$220 for a reman/new alternator.

 

[JusTheUsual]

I know the alternator is working. Batteries haven't been dying. The old one would barely even hold a charge to start the vehicle because the battery cells were messed up. I have a computerized battery charger and tells me the cells were messed up and didn't want to charge it sometimes. The whole battery was screwy. The new one holds charges and volt gage on dash in slightly above middle and never been that high before. I was thinking about maybe possibly but highly doubt it one of the plugs in alternator isn't firmly staying in after putting engine back together and maybe enough to throw a light but I doubt it and will check tomorrow on that. Koda2000 just reminded me about fuses and will check that out also tomorrow. That 130amp alternator is only a year old and like maybe 5k miles at max on it

 

[koda2000]

If the BATT light is on, the voltage regulator isn't turning it off once the alternator is turned on. It means your vehicle is running off the battery. without lights and other accessories on, you can go several days before the battery will finally die. BTW an "messed up battery" can ruin a good alternator because it has too work to hard to keep up with electrical demand. in any event, the voltage regulator (which is part of the alternator) turns the BATT light off by eliminating the ground for the bulb. I've never heard of the BATT light being on if the alternator is charging. something is wrong, perhaps with the voltage regulator. if you have a warranty on the alternator, you may want to replace it.

 

[JusTheUsual]

The reason I don't believe the alternator is dead because the old battery was so bad even over night it wouldn't hold the charge. I drove it for a week so I know the alternator was working charging the battery and the meter on dash was about where it was suppose to be. If the alternator wasn't working the battery would of died when driving it. It really was that bad of a battery. I know bad batteries can destroy a alternator also. So I do know the alternator is charging but obviously something is wrong with light on.. I wll check wires and that fuse you said tomorrow if it aint raining that bad

 

[sgully67]

I would make sure that the battery is being charged. If it is check the connection of single wire connector at the alt. wire color is white with black tracer. If that connection is poor the alt. will still charge but the battery light on the dash will be lit. Very common problem on all Fords with this style alt.

 

[shadowless127]

The only time my battery light came on was right before my alternator died. A bad battery or bad alternator will kill the other one. I had problems with my battery holding a charge a few months before the alternator gave up the ghost. Battery tested fine when I had the alternator replaced, but 5 months later it had issues keeping a charge due to the faulty alternator.

 

[Dan Whitaker]

Check the alternator fuse under the hood. I fought the same issue several years ago and it ended up being a blown fuse.

It started after I had to replace my alternator.

 

[JusTheUsual]

I just made sure the connections on alternator were secure and they were and still battery light. I pushed down on fuses under the hood to make sure they in tight and still battery light. Which one under the hood is the fuse I would check for or should I be checking in the dash fuses also? Any pics for 99 v6 ohv x code would help a lot. I just looked at the sticky/stucky thread up above about fuses and those pics don't look like my fuse box under the hood

 

[Dan Whitaker]

It's a 20 or 25 amp fuse. I haven't had my Mountaineer for 4 years now & I don't remember which # it was. If you have a blown fuse it will be easy to spot.

 

[swshawaii]

Fuse #14 (30A*) Generator/Voltage Regulator

Pages 185-186
http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/99expog1e.pdf

 

[Dan Whitaker]

I just searched my old threads and in my '97 Mountaineer it was a 15 amp (blue) mini fuse in the fuse box under the hood.

Here is the thread http://www.explorerforum.com/forums/showthread.php?t=246387

 

[JusTheUsual]

I just checked fuse and its not blown. dammit. and no corrosion on battery terminal connectors. Installed K&N air filter though but dam cant figure out why that battery light is on.

 

[rego]

Does the battery icon light up with the key in the on position and the motor not running? Icon should be above the speedometer needle.

 

[JusTheUsual]

Yes almost all the lights light up when you switch key on but not engine running but battery light stays on when engine is running

 

[rego]

Not all are on the same circuit. Can't tell from your reply if battery icon lights up.

 

[JusTheUsual]

Yes and battery light stays on when engine is running

 

[fast_dave]

OP - Start with the simple stuff.

I can't tell you how many times I regress back to that ;-)

I've seen internal regulators go bad in relatively new alternators - it does happen.

Save yourself the headache of thinking about all of the complicated causes, first rule out the simple stuff and establish a solid baseline.

Spend 10 minutes, remove the alternator, and bring it to a "big box" parts store that has a computerized alternator tester.

Good luck and let us know!