Battery Light Help

[Schlangenbisse]

Hey guys,

Been a while since I’ve been on here but I would like some help.

My battery light has been on and off for close to 10 months now. Everything I’ve read when searched points to the alternator of course but the car runs flawlessly. I’ve honestly stopped paying attention to it because it’s always intermittent on and off. I have just been waiting for the alternator to fail completely so I can replace it but the car hasn’t skipped a beat.

I’ve had the alternator tested twice before when I first started having issues and both times it can back fine.

Do we think I should just bite the bullet and replace the alternator in hopes it will fix it? This will be the second alternator in the 8 years I’ve owned the car. It’s a factory reman.

Thank you for your help!

 

[John M]

Did you try checking it when it’s loaded ( all accessories on) and wiggle the harness, I have the factory Ford wiring books at home if you want to ohm the wire to the light let me know if you need some pics

 

[Schlangenbisse]

Did you try checking it when it’s loaded ( all accessories on) and wiggle the harness, I have the factory Ford wiring books at home if you want to ohm the wire to the light let me know if you need some pics

I haven’t tried this no. I would love some pics thank you!

 

[01yellercobra]

When does the light come on? Does it come on more when everything is hot? I had an alternator that worked fine when cold and would pass the load test. But once it got hot after driving for a while it would lose its charging ability.

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[Schlangenbisse]

When does the light come on? Does it come on more when everything is hot? I had an alternator that worked fine when cold and would pass the load test. But once it got hot after driving for a while it would lose its charging ability.

Sent from my SAMSUNG-SM-G935A using Tapatalk

There is absolutely zero pattern or instance that makes the light come on or go off. I’ve tried everything to reproduce the light coming on. It just lights up whenever it feels like it. It never stays on for more than a few mins.

 

[01yellercobra]

I think it's the green wire down by the plug that powers that warning light. It might be worth making sure it has a good connection.

 

[ccq8le]

When does the light come on? Does it come on more when everything is hot? I had an alternator that worked fine when cold and would pass the load test. But once it got hot after driving for a while it would lose its charging ability.

Sent from my SAMSUNG-SM-G935A using Tapatalk

I have had the same issue before. It took me a while to lick it. Light would come and go and on hot days it would come on more often. Sometimes if I rev'd up the engine the light would go off.

Only thing that fixed it was new wires and a new ALT and I haven't seen it come on again.

The cigarette lighter voltage gauge come in handy for this kind of diagnosis.

 

[Schlangenbisse]

I think it's the green wire down by the plug that powers that warning light. It might be worth making sure it has a good connection.

Down by which plug? The harness that goes to the back of the alternator?

 

[01yellercobra]

Down by which plug? The harness that goes to the back of the alternator?

Yes. That one.

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[*Jay*]

Down by which plug? The harness that goes to the back of the alternator?

It comes off of the main power output line by the 2 fusible links near the 12v distribution lug and goes up to the fuse box in the engine bay. Its the light green wire in this diagram. Check this wire for a good connection near the fusible links.

 

[*Jay*]

Yes. That one.

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If that wire (grn/red) had a loose connection the battery light would not turn on when an error was encountered, if the light green wire I just posted has a bad connection it will trigger the battery light when connectivity is lost.

 

[John M]

Just got home looks like you got them