1993 Headlight/dome/cig lighter circuit repair options, help needed.

[WarWagon]

1993 Headlight/dome/cig lighter circuit repair options, help needed. Continuing to solve the issue after a battery failure started here.

So far I have a 0.8v drop to the cigarette lighter with the high beams on and the dome light on. I found the harness behind the fuse panel in the lower left dash going past the headlight switch wire breakout is 5 degrees hotter than everything else. Fusible link is "cold" as measured with a IR gun. All of these are on the same wire off the passenger side positive "bus" bar.

No voltage drop that matters to the bus bar.

Wiggling the harness behind the fuse box gives me .2v difference in readings. Clearly the wire or splice is burning out or corroded and burning up.


I need to know what is all on this circuit so please point me to a schematic for the 1993.

What is the best way to repair this? I assume GM has a mega splice by the headlight switch wiring breakout of the main harness going to all the related fuses? IS there a "kit" to replace this wire and breakout or a better way to go about it? Junkyards to LMC truck / Painless kit parts are welcome suggestions. Is there a weak point I am overlooking on this circuit like the headlight switch breaker etc?

It's too late for the headlight relay mod to completely fix the issue, but, I will be adding it as part of the repair.
http://www.thetruckstop.us/forum/showthread.php?34064-Headlight-mod-s&highlight=headlight+harness

 

[Diesel Nut]

Hope this helps. I would recommend replacing the wire and getting the head light harness. Would also check for other wire while under there, never know with older vehicles.

 

[Diesel Nut]

View attachment 42377View attachment 42378View attachment 42380 Hope this helps. I would recommend replacing the wire and getting the head light harness. Would also check for other wire while under there, never know with older vehicles.

 

[Diesel Nut]

 

[Diesel Nut]

If you need anything else let me know I'll see if I can get it. I have a account with Alldata.

 

[Twisted Steel Performance]

I just purchased a new HD 4hi headlight harness from a fella on another forum, very stout plug & play from the bulk head forward, if ya need the info let me know.. He also does any custom harness to order..

 

[WarWagon]

As always this is a work in progress. It's the next project to get done on the 1993.

 

[WarWagon]

I'll post pics later. The biggest problem with schematics, diagrams, "we tore the truck down to make this manual" (Haynes) is complete and utter lack of anything "useful" to find the actual damned wire, connectors, and ground locations. All it does is tell you what all is on the wire. I would love to see electrical taken a step further with a picture of connectors and their locations in harnesses etc. Maybe Alldata has this and I haven't looked. Haynes and other off the shelf books are not useful in this regard.

First I pierced the wire after the fusible link on the engine side passenger firewall to make sure it wasn't the link under full load. I had pulled all wires off and reattached one at a time to isolate the dome /headlight/cig lighter power wire from the power block. I should have followed the fusible link wire past the first tape wrap in the harness on the firewall. More on that later.

After pulling the driver side cab connector apart and finding nothing hot or burnt I had no choice but to follow known wires. I started with the batts disconnected and then knocked the fuse panel into the dash. I then cut the tape off the wire harness till I found the splice for the headlight switch power. One wire going to the headlight switch and one wire going to the fuse panel. The 3rd heavier wire went toward the passenger side of the truck. This contradicted the assumptions I made from the stuff provided that it went through the driver side cab connector.

I then went back to the fusible link and traced the wire to the passenger side pass-through. Looks like 2 power wires go through it, HVAC power being the other, assumed. The pass through looked funny so out came the coolant overflow for a better look. Just dirt buildup.

Next, the glovebox came out. Here we have the HVAC 2 wire connector and the wire I am tracking on a separate 4 wire connector. The 4 wire connector was wrapped in foam to keep rattles down. I received a minor burn while unwrapping the foam from the connector. The firewall side of the connector wire is hot, yet, the other side of the connector wire isn't.

Looks like I caught it in time before the connector melted down. I am not sure what I am looking at for the failure at the moment but it was late so I gave it up for the day. Maybe the wire and terminal is the actual issue not the connector?

 

[WarWagon]

Here we go:


Issue at hand. Batteries are 12.6 - 12.8v with 12.4v at distribution bus.



Assuming this splice was the issue. But the wires go to the headlight switch, fuse panel, then cut across to the passenger side. Thus power is supplied from passenger side.



Pass through showing this red wire and the other that goes to the HVAC system. Dirt made it look funny so I took a closer look.



Connector in question behind the glove box.



Cleaned connection and still have a voltage drop heating issue on the passenger side wire. The crimp or wire at crimp has high resistance. Note HVAC connector also disconnected for cleaning.

 

[WarWagon]

Finishing up with the repair some time ago...
Soldered the wire with aluminum foul as a safety to catch any solder "drips".

 

[WarWagon]

And it never Fing ends! More electrical repairs... Complete rewire of AC compressor, high pressure cut out, diode, and other wires including new wire on the important grounds and half assed tape on WIF sensor and fuel heater. The AC high pressure switch burned up on me as the diode was further back in the harness so the High pressure cut out would spark every time it opened. Fixed that issue now.