1998 Mustang Gt cannot get alt to work - Ford Mustang Forum

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post #1 of 3 (permalink) Old 11-16-2012 Thread Starter
money_pitt2's Avatar
Joined: Oct 2012
Location: NORTH East ga
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Unhappy 1998 Mustang Gt cannot get alt to work

i have a 98 gt and i cannot get my alternator to work for more than maybe 3 miles.
I bought the car 8 months ago and it never read past the R of NORMAL, but car started right up no light surging, power loss, or anything then one day car just dies i figure ok alt went out. So i buy a new battery and alternator and install car runs fine but still dosent rise above R so i started replacing some of alt wires no luck there. Took old alt and battery had both tested both were fine, battery was dead but had it charged and installed in different car it does fine. now my car has started acting up again and ive tried battery and alt again and some wires but after 2 or 3 miles gauge drops off and car starts to die. no battery light had everything tested and its all fine but im loosing my mind with this please help

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post #2 of 3 (permalink) Old 11-17-2012
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OK, if you get no alternator light that might just be the problem or at least the clue on how to fix it. The alternator light bulb provides resistance and triggers the alternator's voltage regulator to sense load.
On the circuit board the bulb mounts to is a resistor. If the bulb goes out the resistor acts as backup if the bulb burns out. Rarely do both go out.

Does the alternator light come on with the key in the on position? If it does then we can probably look elsewhere.

The wire on the alternator that goes to the bulb/resistor is green/whit stripe if I'm not mistaken.


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post #3 of 3 (permalink) Old 11-17-2012
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+1 on above.

Just wondering if you have checked the fuses in the engine bay and driver's kick panel? For example the "ALT" fuse in the engine bay and I/P Fuse #18.

Since this is a "new to you" car, confirm that the grounding strap is in place between the left hand motor mount and the frame rail. It should be a bare braided line. Also check the battery terminals and the grounds around the radiator core support. Are they clean and tight?

Are you positive the correct alternator for your application has been used? There are differences between some Ford products in the alternator's internal wiring.

To the small alternator plug should have two wires (Y/W and LG/R) verify that the W/BK jumper is in place.

Confirm that the fusible link is good. Disconnect the alternator's main B+ terminal. Confirm there is +12 volts on the line. If not, suspect a bad fusible link.

The wire that goes to the alternator charge warning light is LG/R for the 1998 model year.

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