Need info on fusible link.

[runningiron]

I had to replace my flexplate in my 1977 Chevy 1/2 ton pickup 350/350. Rather than completely take the tranny out I loosened up the tranny bolts and slid it back enough to unbolt the cracked flexpate and replace it. I might have disconnected a wire in the wiring loom and I have no juice going down to the starter. More than likely it is a fusible link closer to the starter. My question is, what size wire is the small lead closest to the block that attaches to the solenoid? I have some fusible link material and wanted to replace it as the original is oil soaked and brittle. It had separated one time prior, was not burned up and just spliced it to keep rolling. I never really noticed fusible links near the starter in all the clunkers that I have driven in the past. Do I need a fusible link? Anyone know what size wire that might be? Thanks for your help. Runningiron

[ray_mcavoy]

Stock 77 wiring has 3 wires attached to the starter solenoid:

(1) Positive battery cable.
(2) A 14ga red fusible link wire that connects to a 10ga red wire. This should have a large ring terminal and connect to the large stud along with the battery cable. The other end of the 10ga red wire connects to the junction block on the firewall.
(3) A 12ga purple wire connects to the "S" stud on the solenoid ... that's the small stud that's closest to the engine. There is no fusible link in this wire. And this wire should only be live when cranking the engine (ignition switch in the "start" position).

Originally Posted by runningiron

Do I need a fusible link? Anyone know what size wire that might be?

Yes, you need a 14ga fusible link on the 10ga red wire that connects to the large batt stud on the starter solenoid. This wire is used to feed battery power to the rest of the truck. And it's part of the charging circuit that connects the alternator to the battery. Without a fusible link in this wire, a short circuit can burn up the entire wire along with any other wires bundled together with it in the harness, making a big mess and potentially catching the truck on fire.

The 12ga purple wire doesn't have it's own fusible link because the ignition switch receives it's power from a 12ga red wire that leads back to the junction block on the firewall. And that wire is protected by a 16ga fusible link where it connects to the junction.

[slimneverdies]

Originally Posted by ray_mcavoy

Stock 77 wiring has 3 wires attached to the starter solenoid:

(1) Positive battery cable.
(2) A 14ga red fusible link wire that connects to a 10ga red wire. This should have a large ring terminal and connect to the large stud along with the battery cable. The other end of the 10ga red wire connects to the junction block on the firewall.
(3) A 12ga purple wire connects to the "S" stud on the solenoid ... that's the small stud that's closest to the engine. There is no fusible link in this wire. And this wire should only be live when cranking the engine (ignition switch in the "start" position).


Yes, you need a 14ga fusible link on the 10ga red wire that connects to the large batt stud on the starter solenoid. This wire is used to feed battery power to the rest of the truck. And it's part of the charging circuit that connects the alternator to the battery. Without a fusible link in this wire, a short circuit can burn up the entire wire along with any other wires bundled together with it in the harness, making a big mess and potentially catching the truck on fire.

The 12ga purple wire doesn't have it's own fusible link because the ignition switch receives it's power from a 12ga red wire that leads back to the junction block on the firewall. And that wire is protected by a 16ga fusible link where it connects to the junction.

Would what you're talking about cause this to happen???


I'm getting no starter noise at all and the wire that you see that's exposed seems to start smoking a little when I turn the ignition. This just started happening last night and I replaced the starter a week ago...

[runningiron]

Ray,
Thanks alot for the info. Very clear even to a dummy like me when it comes to wiring. Have a great weekend.
Bob aka: Runningiron

[Oldriginal86]

Make sure no wires got pinched when the tranny was tightened up. First hand experience.

[runningiron]

Yep, I checked for pinched wires. I crawled underneath it and found 2 crusty starter wires that were broken underneath some tape. I think I'll be back in business tomorrow. Thanks