So, what am I looking for that is causing the link to burn? The headlights were turned off when it was smoking. Did I somehow fry the headlight switch from leaving the lights on all day? Would this be causing a short and burning the fusible link?
Ideas?
Without seeing the actual installation or a detailed schematic of the wiring I am shooting from the hip, but:
It is my understanding of this modification that - when completed - the dash mounted (i.e. stock) H/L switch is no longer part of the power supply circuit to the head lamps.
At that point it's sole function is as a control device - to supply a minimal amount of power required to energize the relay coils and pull in the relay contacts.
The current required to actually illuminate the sealed beams is supplied from a source external to the OEM wiring (like in your case, the FW mounted junction block). It then passes through a set of dedicated fuses. Next it flows through the relay contacts. Finally it continues on to the actual lamps. Correct?
But:
1. If the power to the headlights (via the fuses/relays) is tapped off the actual junction block (at one of the studs) at a point "upstream" of the fusible link
2. And the fusible link that is connected to the JB does not even feed the H/L switch. The feed to the headlight switch (also ECM, T/L,courtesy lamps, dome light, etc - in other words the left hand side of the fuse block) has only one fusible link - and it is located down at the solenoid.
The link at the firewall - next to where the power for the headlights is tapped - supplies a lot of things including the ignition switch - but not the headlights.
Also, there is this strange aspect:
But, while it was idling, I noticed the fusible link from the junction block at the fire wall started to smoke. I turned it off, checked for exposed wires, found nothing. Started again, waited 30 seconds and noticed the link started to smoke again. turned of the truck again. Decided to pull the fuses for the headlight relays since that was the reason my battery died and the fuse block for the headlight relays gets its power from the junction block. started it again, no more burning link.
I can imagine several different scenarios where engine operation might cause that link to overheat - considering that it is feeding the ignition switch and consequently everything that is fed from the ignition switch.
But how did the act of pulling the fuses (for dedicated power supply to the head lamps) seem to be the final solution to the problem?
And, again how is engine operation involved? I think it isn't because the engine was shut down that the problem went away. Rather it is because the key was moved to the OFF position.
Seems that there are two ways to resolve the over current condition through that FW fusible link:
1. Cut power off to the entire IGN bank of the fuse block - by turning the key to OFF
2. Cut power to the headlights by pulling the fuses in that particular branch circuit.
Dude, I wish you luck! Maybe it would be best to work backwards on this one:
Starting at the headlight end, check the wiring and control devices for a dead short to ground in a section by section fashion. Best done by separating the leads at convenient places and locating the grounded section by listening for the "beep" with your Fluke.
