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Discussion Starter · #1 ·
I have a 2002 mustang 3.8L and i had the alternator burn up on me so i replaced it and the battery and about a week later the new alternator went out so i replaced it and it seemed to be working fine but the battery light stays on! The gage is in its normal running spot and runs normal but then the other day i was driving and all the gauges stopped working along with the radio and a/c but the car kept running strong then a few moments later everything went back to normal! any suggestions on what might be the problem or where to start looking? oh ya and after i put the second alternator on i had the electrical checked by the people at napa and they said everything was working fine.
 

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Welcome to AFM. :wavey:wavey

Not exactly positive on your problem but does that alternator have an external voltage regulator or is it built in. Something is causing the altornator to short out.

Soooo.... I may not have really helped you but you chose the right place to ask questions.:bigthumbsup:bigthumbsup
 

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Take it to advance auto or any parts store that does free alternator and battery testing!
 

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Discussion Starter · #5 ·
I had them both tested again and they are both fine. and everything seems to be working fine on the car. its almost like it has a mind of its own!
 

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If you are getting voltage surges, you have to look at the wiring going to and from the alternator. Also check your terminals. Check your PDI box for loose connections.

The surging is coming from the car running off the alternator, and not the battery.......
 

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i am having the same kind of problem. i have a 97 mustang and the battery light is on. so far i have replaced the battery, the alternator and the wires that connect the two. my terminals are on tightly. i have no idea why the battery light is still on. does anyone have any suggestions on what to try next?
 

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Going to assume that the battery and the alternator are confirmed working.

Absolute first thing. Confirm that all battery cables are clean, tight, and corrosion free. Don't cut corners here. Don't ignore the corrosion cauliflowers growing on the battery terminals.

Confirm the fusible links are good between the alternator B+ and battery positive. Disconnect the alternator B+ and measure the voltage. Compare the voltage directly on the battery positive. Should be the same. If not, the fusible links are bad.

If bad, the fusible links are not normally servicable. A new battery cabel is the usual repair.

Check the small wire connector at the alternator. Look for bent/pushed pins. Is the connector clean? Does it fit tight?

Pay special attention to the LG/R wire as this is the battey charge warning light. Any breaks in this wire will cause the battery warning light to come on.

For the 99-04 MY, confirm fuse F1.20 and F2.5.
F1=BJB=Battery Junction Box-located engine bay
F2=CJB=Central Junction Box-located driver's kick panel

Here's a link for the 1999-2004 Fuse panel schedule.
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271

For the 96-98 MY, confirm the alt fuse in the engine bay and I/P fuse 18 in the driver's kick panel.

Confirm means more than just "look at it". Pull the fuse and test with an Ohm meter.

Check the main terminal to the battery junction box in the engine bay. Ensure the bolt and cable are tight and clean.

Check the grounding strap between the motor mounts and frame rails. With the key off, measure the resistance from the alternator case to battery negative. Should be low. Post.

Start the car and measure the voltage at the battery. Post. Repeat the measurement at the alternator B+. Post.

Turn the head lights on and repeat the above measurements.
 

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Battery Light

Could it just be a code that hasn't been cleared? As in an OBD2 code that is stored causing the light to go but there is nothing wrong. It will continue to be on until someone clears it even though there is no problem. Just a possibility?
 

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I was going to suggest the code to be cleared too, but I just thought, are you 100% sure, the battery and alt, are designed for ur particular model? A wrong battery would throw the code...

Sent from AutoGuide.com Free App
 
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