Unusual Battery Light Issue. Have searched and troubleshot

[Formula51]

Need some help. I have had a battery light that comes on a short drive after startup, typically less than a mile. It will go out in a mile or so, sometimes flickering in and out, and then stay off for good. It usually only does this when the engine is cold.

It has been doing this for OVER A YEAR.

Here is what I know:
- Battery is Optima Red Top and tests perfect. Terminals clean and tight.
- Alternator is stock and load tests perfect at auto store.
- I have a voltage meter that plugs into cigarette lighter near shifter and it reads 13.4 to 13.7 volts all the time, even when battery light is on.

If the car is not undercharging or overcharging, then why is the light coming on? If it was a stuck voltage regulator, wouldn't I see it overcharge when On?

Thanks in advance for your help.

 

[1wild-horse]

May be a bad spot in the wire leading to the cluster, or the regulator is junk.
Check fuse 20 in the box under the hood. Make sure its not loose. The yellow wire with the white stripe in the voltage regulator plug should be checked too. See that the terminal is not spread.

 

[jbou91]

Check the pigtail going to the alternator, mine was broken on the inside that would cause the battery light to flicker sometimes. Would charge normally too

 

[roy_1031]

Mine had the same issue when I bought the car. The previous owner said he took it to the dealer and couldn't diagnose anything. Everything was fine and within spec on the charging system. I drove it like that for about 3 or 4 years and never had an issue. I finally got rid of the light when I upgrade blowers added a 3.2" alt pulley and had the alternator for piece of mind. It was just one of those gremlins that was hidden in the corner and didn't effect anything.

 

[Formula51]

Thanks for the thoughts. I will do the checks mentioned above. Any chance this could be a ground issue?

I have noticed that sometimes I get a small shock if I put my hand on the rocker or quarter panel when getting out of the car. I have always attributed this to static electricity from sliding across the suede seat inserts, but maybe not. I have checked that all of my grounds are clean and tight, but not metered them as I have seen mentioned in a search.

 

[hotcobra03]

Crazy. .

Alt being most common to cause light on dash.

Have you had radio go black than back on?
Gages sweep while driving?

Are battery terminal's original?

After 13yrs of daily driving mine these were some of my issues..

Caused from bad alt,battery or ground wire

 

[Formula51]

Crazy. .

Alt being most common to cause light on dash.

Have you had radio go black than back on?
Gages sweep while driving?

Are battery terminal's original?

After 13yrs of daily driving mine these were some of my issues..

Caused from bad alt,battery or ground wire

No to the radio or gauges sweeping. Battery is an aftermarket Optima Red Top. I believe the leads are original.

Car does have an HID kit put on by previous owner, but added wires are clean and tight (I checked) and I have no dimming of lights.

 

[Formula51]

Another thought. Car has Ford GT pumps and BAP wired full on. Has the wiring upgrade to the trunk. Could it be related to current draw? Although I would think that would show up immediately on startup, not half a mile down the road.

One more thought. When I replaced the radiator cooling fans due to a cracked housing, the new fan unit had a new resistor? (Cylindrical piece the wiring harness plugs into). I did not have the light come on for several months after that.....but then it started doing it again.

 

[hotcobra03]

Another thought. Car has Ford GT pumps and BAP wired full on. Has the wiring upgrade to the trunk. Could it be related to current draw? Although I would think that would show up immediately on startup, not half a mile down the road.

One more thought. When I replaced the radiator cooling fans due to a cracked housing, the new fan unit had a new resistor? (Cylindrical piece the wiring harness plugs into). I did not have the light come on for several months after that.....but then it started doing it again.

What alt is in car?

Iirc ..this is an issue on higher amp ..

There is a thread on site about it

 

[Formula51]

What alt is in car?

Iirc ..this is an issue on higher amp ..

There is a thread on site about it

Stock alternator.

 

[Formula51]

May be a bad spot in the wire leading to the cluster, or the regulator is junk.
Check fuse 20 in the box under the hood. Make sure its not loose. The yellow wire with the white stripe in the voltage regulator plug should be checked too. See that the terminal is not spread.

Update: checked fuse 20, it was not loose or bad but replaced it with a new one to rule out. Checked the yellow wire with white stripe in the voltage regulator plug, all looked good. Cleaned with electrical contact cleaner and reassembled. Also cleaned the pigtail connection to the alternator (was just a little rusty) and the connection of the ground wire to the frame on the driver side. Made sure all my grounds are clean and tight, including the strap to the motor mount on the drivers side.

Light still came on after a few minutes of driving (voltage reading 13.5 to 13.7 the entire time) and then went off. Flickered on once or twice more and then stayed off for good like it has been doing for over a year now.

Any other ideas?

 

[1wild-horse]

My next step would be to load test the indicator light wire, lg/rd in the regulator plug all the way to the cluster. It passes through 2 inline connectors on the way. If there is resistance in the circuit anywhere it could cause this. If the wire comes up clean then I would say put an alternator on.

 

[Formula51]

My next step would be to load test the indicator light wire, lg/rd in the regulator plug all the way to the cluster. It passes through 2 inline connectors on the way. If there is resistance in the circuit anywhere it could cause this. If the wire comes up clean then I would say put an alternator on.

Can you provide details on how to load test the wire?

 

[1wild-horse]

Load testing a circuit is a better check than checking ohms on a wire because it tests the wires ability to carry voltage/amps.
You can mock up a simple 3157 bulb with two leads coming off.
Then basically you isolate the wire by unplugging both ends, connect a jumper wire to ground and the other end to one end of the circuit you are testing. Connect one lead from the bulb to the other end, and the other end to 12 volts. If the bulb lights brightly, the wire is good and free of resistance.