Alternator fuse keeps blowing

Tiny
BRIDGES77
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  • 1998 FORD MUSTANG
  • 4.6L
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Battery light came on one day. About a week later it shut off on the way to work. Found the alternator fuse blown. Replaced the alt thinking it was inside the regulator. Also changed out the starter and battery. Fuse blew again. It blows at different times so hard to tell what’s going on. Please help
Saturday, December 28th, 2019 AT 12:09 PM

31 Replies

Tiny
ASEMASTER6371
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Good afternoon.

What is the fuse number that keeps failing?

Roy
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Saturday, December 28th, 2019 AT 1:22 PM
Tiny
BRIDGES77
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The alternator fuse here bottom left corner.
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Sunday, December 29th, 2019 AT 9:07 AM
Tiny
ASEMASTER6371
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Can you please give me the fuse number? It is way too small to read on that picture.

Roy
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Sunday, December 29th, 2019 AT 9:13 AM
Tiny
BRIDGES77
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I think it is #14. It is under the hood fuses. Takes a 20 amp fuse and is labeled alt.
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Sunday, December 29th, 2019 AT 9:29 AM
Tiny
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Okay, check the yellow wire at the alternator. Does it have power with the key on?

If it does not, then we are at the issue. If you have replaced the alternator, then either the alternator is bad again, which I doubt, or you have a wiring issue.

Roy
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Sunday, December 29th, 2019 AT 9:41 AM
Tiny
BRIDGES77
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Unfortunately the battery is dead now. I would have to get back to you with that info. So if no power at the yellow wire, would that be the wire to inspect inside the loom for a short to ground?
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Sunday, December 29th, 2019 AT 9:50 AM
Tiny
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That is correct. That fuse only controls that wire from the fuse box to the alternator.

Roy
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Sunday, December 29th, 2019 AT 9:54 AM
Tiny
BRIDGES77
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Sweet and that is why it won’t charge the alternator? Thanks
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Sunday, December 29th, 2019 AT 10:23 AM
Tiny
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Correct.

Roy
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Sunday, December 29th, 2019 AT 10:29 AM
Tiny
BRIDGES77
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Thank you so much!
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Sunday, December 29th, 2019 AT 10:29 AM
Tiny
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You are welcome.

Always glad to help.

Roy
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Sunday, December 29th, 2019 AT 10:32 AM
Tiny
BRIDGES77
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Update. The battery is charged now. Key on or off it instantly blows the fuse.
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Monday, January 13th, 2020 AT 2:26 PM
Tiny
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Okay, do the checks I suggested before you charged the battery.

Roy
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Monday, January 13th, 2020 AT 2:49 PM
Tiny
BRIDGES77
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Say what?
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Monday, January 13th, 2020 AT 2:53 PM
Tiny
BRIDGES77
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I charged the battery then tried to do the test. No power at the yellow wire but the fuse is blow and keeps blowing as soon as I put one in.
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Monday, January 13th, 2020 AT 2:58 PM
Tiny
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Disconnect the yellow wire from the alternator and see if the fuse still fails.

Roy
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Monday, January 13th, 2020 AT 3:24 PM
Tiny
BRIDGES77
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With the yellow wire unhooked it does not blow now.
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Monday, January 13th, 2020 AT 3:49 PM
Tiny
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Do you have power to that wire with it disconnected?

Roy
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Monday, January 13th, 2020 AT 4:08 PM
Tiny
BRIDGES77
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Yes about 9. Volts?
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Monday, January 13th, 2020 AT 4:17 PM
Tiny
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You should have battery voltage. If your battery is charged, it should be 12.6 volts.

If you hook that wire up, and the fuse fails, it points directly to the alternator.

What brand alternator did you use to replace it?

Where did you buy it?

Roy
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+1
Monday, January 13th, 2020 AT 4:26 PM

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