1981 F250 electrical problem

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Mar 1, 2026 | 08:22 PM

#31

JimsRebel

Cargo Master

Joined: Mar 2008

Posts: 2,564

Likes: 207

From: Washington

On this link...
https://www.garysgaragemahal.com/cha...tribution.html

Fuseable link "J" depends on the alternator size, with AMP METER
Either 14 ga or 16 ga

Also, for reference, the splice that failed is S201

Jim

Mar 1, 2026 | 08:28 PM

#32

arazu

Thread Starter

Mountain Pass

Joined: Jul 2014

Posts: 102

Likes: 2

The wire is black from the solenoid to the splice and black on the other side of the splice. The schematics I have show black/orange but I didn't see any orange.

I'm also not sure if the diagram I'm looking at is accurate to my truck. It doesn't show the red wire.

I haven't changed the alternator but I doubt it's original. I'll check in the morning.

Thank you.

Mar 1, 2026 | 08:31 PM

#33

arazu

Thread Starter

Mountain Pass

Joined: Jul 2014

Posts: 102

Likes: 2

Quote:

Originally Posted by JimsRebel

Thank you again. I'll check alternator size.

I think I have an amp meter because the needle is in the middle with no power like you mentioned.

Mar 1, 2026 | 09:51 PM

#34

BigBlue2

Lead Driver

Joined: Apr 2002

Posts: 5,278

Likes: 1,233

Did you find a strange relay? Could it be the horn relay? They used a horn relay in 1980, but you might have some 1980 wiring if your build was close to the change over.

Mar 2, 2026 | 07:32 AM

#35

Franklin2

Moderator

Joined: Jan 2001

Posts: 56,979

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From: Virginia

Quote:

Originally Posted by arazu

Looks like that was a splice in your first posts. If you are still missing a main fusible link, you can substitute a large mega fuse. I think the largest alternator offered on these trucks was a 70 amp. So a 90-100 amp mega fuse should do the job.

Mar 2, 2026 | 11:14 AM

#36

arazu

Thread Starter

Mountain Pass

Joined: Jul 2014

Posts: 102

Likes: 2

Quote:

Originally Posted by BigBlue2

Did you find a strange relay? Could it be the horn relay? They used a horn relay in 1980, but you might have some 1980 wiring if your build was close to the change over.

Jim was asking about it. I think it's either horn or marker lights.

Quote:

Originally Posted by Franklin2

Thank you. I'll get one of those.

Quote:

Originally Posted by JimsRebel

Thank you for all the help, information, and photos.

A big thank you to everyone else as well.