Alternator Fuse blowing above 3000 RPM

Jules98GT

New Member
Apr 4, 2021
3
0
1
30
Indiana
Hi all I am new here and look forward to sharing all my adventures lol

I have a 1998 Mustang GT.

I've run into an issue where above 3000 RPM the alternator fuse is blowing. That the 20 amp one in the engine compartment.
I have tried 3 alternators. All with new rectifiers.
I've replaced the fuseable link, and replaced the 3 wire connector at the alternator. yel/wht, grn/red/ blk/wht
I have NOT replaced the blk/wht wire that is apart of the rectifier circuit.

Before i start replacing the wiring in the charging circuit all together I wanted to ask a few questions.

I noticed two connectors under the fuse box, same colors as the rectifier wires. Is this how we get from the blk/org wire to the yel/wht wire?
Where is this change made?

This circuit is stupid simple.

Thanks!
 
  • Sponsors(?)


Jules98GT

New Member
Apr 4, 2021
3
0
1
30
Indiana
Update: Replaced charging wire, I also took apart the fuse box to check the terminal connections. The terminal for that fuse is a little loose. I re-seated it and put it back together.
Fresh set of battery cable ends, a new belt tensioner and belt

Started the car reved it up and WOILA all good.
Let the car warm up and reved it again and it popped.

What is going on here?

Ohm readings are as follows.

Battery to Alt - 0 ohm
Yellow/White wire to fuse block - 0 hm
Ground terminal to alternator body - 0 Ohm.

Thanks in advance.
 

TrippleBlack

New Member
Jun 21, 2021
1
0
1
35
Florence, AL
I'm dealing with a similar issue in a 97 gt. My charging system quit while driving. I thought it was the alternator because the belt had been slipping. I put a reman on and it did no good.

Then I heard about the alternator fuse. That little alternator fuse had blown. Replaced it and things seemed right.

I was driving the next day or two with the air and radio on and lost charging again. But there was a much bigger event this time; the engine stalled for several seconds and then came back to life while coasting. I ran on battery power about 10 miles home.

This time I found that the alternator charging cable had grounded to the alternator bracket, which may have caused the fuse to blow the first time. A hole had been rubbed through the alternator boot allowing the cable connector to ground out. At the same time, my fusible links were burned out from the short.

This event destroyed my alternator. The internal connectors from the rotor to the slip rings erupted and the insulator blew up.

I've now installed a new alternator and new 4 gauge power wires with a 200 amp fuse from the alternator to the power block. And have added new 4 gauge ground wires from the alternator bracket to the engine to a factory ground point. The battery is about 6 years old, fully charged, and tests good.

I've cranked and idled/revved for some time in the garage and things seem to be working correctly. I haven't had a chance to drive at length but will update if not solved.
 

Attachments

  • IMG_20210620_201223169.jpg
    IMG_20210620_201223169.jpg
    686.1 KB · Views: 4