Fusible Link Burnt….why?

[westie47]

I started another thread about it but the culprit was the engine wiring harness. The low beam wire (violet) and fusible link were in the opposite positions. This caused the power wire on the dash side to connect to the violet wire on the engine dude. The dash side power wire melted/burned back about 1.5 inches. It was a brand new harness too! FML

 

[Nacho-RT74]

well, as mentioned at the other thread... if you have two wires mismatched ( one on each side of firewall ) you actually have at least 4 wires mismatched... at least two at each side of firewall... Maybe even more, because there is no way to just get one wire mismatched at each side.

The good on this is you are on the track without ( apparently ) a bigger damage.

That red wire seems to be the batt wire, the one which should get the fuse link. Hence why you don't have ammeter reading. The ammeter is actually a batt status gauge ( geting charge or discharge ) depending on alt capacity.

The violet wire is the temp sender wire, which handles negative/ground sourced by the sender, which even with low resistance reading ( low temp ) around 70 ohms will produce a short (Is like a Bulb, which is a controled short) somewhere along the line... so that explains the fuse link fail... and some other fails per what I have found on your other threads.

Now, which other wires are crossed? maybe just those two on the cab side mismatching the two on engine bay side? Or some other?

 

[Nacho-RT74]

Dunno which exactly car are you working on but it seems to be a 68/70 ?

this is a 68 B body bulkhead close up... you can see there the colors and cavities on bulkhead. Some diff can be found between 68/70 on electrical but won't get mismatched circuits anywhere at bulkhead between those years as far I know, like 71/74 does, because extra accesories wires such as hideaways on 70s or clutch ground or reverse dash source run throught the firewall with grommets.

 

[Nacho-RT74]

I think the only diff could be found on 68/70 production is the back up lamp circuit on 69/70 againts 68s, but those are on to the wiper harness plug, not on engine or forward light harness. Pretty much sure those share the same disposition on bulkhead on all 68/70, althought not necesarilly same harness due diff sockets, lenghts ( BB or SB ). Need to be checked anyway.