Shawn Stanford

All that is correct.

Your questions:

• If you unplug the lamp control until and turn the parking lights on do you have left front and side marker lights? Right side should be on Yes, I have front right marker lights with the LCU unplugged.
• If you plug the lamp control unit back in and unplug T4g which is wire in left fender that goes to the left parking and side marker light do you have rear left side and rear left marker lights on? No. with the LCU plugged in I don't have rear right marker lights.
• When you jumpered the light control module in the 84 thread (1-9-12) brake lights, (3-5) rear right markers, and (4-7) rear left markers you said that all of your lights worked? Yes, with the LCU connector jumpered, I have all the rear marker lights and brake lights.

The rear of the car is good now that I have removed and jumpered the LCU. I just jammed some wire in there to test, but I have some male bullet connectors on the way for a permanent solution.

The headlight and front marker light circuits run together all the way to the fender. I traced the harness from the front right corner to the fire wall and I don't see any breaks, frays, or chewed sections. I looked behind the CE panel and everything looks okay going into the firewall.

At this point, unless a miracle occurs soon, I'm going to run new wires up to the left corner for the low beam and marker light circuits and call it done.

Mrmerlin

Usually the wires get cut at the metal anchor clamp under the headlight wherethe harness t flexes make sure the side marker is also properly connected at the junction block and the light housing

Shawn Stanford

Thanks, Stan. I was up in the fender and it all looks good in there. I already unplugged the wires going into the splitter block for the side marker and the front running light and deoxed the wiring. I'll look again (why not?), but I'm pretty sure it's good.

Mrmerlin

Shawn the failed wire will be inside the black harness shield ,
so you wont see it ,
but if it has occurred thats the most probable place to start your search,
thus it requires cutting the sheathing open.

BUT before you do,
remove the front block off plate,
and turn on the lights,
and then move the harness around near that clamped area
you might also notice how tight the harness is with the lamps raised,
if its tight the chances are better this failure has occurred.

NOTE see if you can change the flex points by adding some slack to the harness between the clamped areas.

NOTE while moving the harness around you should see one or both of the lamps come on

Shawn Stanford

Oh, golly. I really don't want to cut into the wiring harness...

Anyway, I looked at the harness in the fender and there's a nice curve of wire below the headlight when it's up, so no stress there. I flexed it and shifted it where it goes into the grommet through the fender and I didn't get any of the missing lights (low beam and marker lights) blinking on. The harness is attached very solidly to the car where it crosses the front from right to left, I don't think I could move it if I tried without taking the entire front of the car apart..

Geo55

If you didn't find the problem elsewhere, you should take Stan's advise into consideration. I believe that he has experience.

Mrmerlin

there should be a metal tab that was bent across the harness sheathing,
this was to hold the harness to the frame,
thats just under the headlamp unit,
the harness flexes at this point and the wires eventually break.

ZEUS+

Locating an open circuit can be a tedious task. Unless the open/broken wire is easily visible, it's a search mission. You have to follow the path of power from source to open/break. Wires can break inside the insulation and looks can be deceiving. If you run new wire, completely remove the old wire from circuit.

Shawn Stanford

I found the tab in the fender and pulled the harness out to visually inspect it and flex it (to check for flashes in the headlight). No dice, and I don't see any breaks or frayed spots in the fender.

SwayBar

Have you been able to check the continuity of the wires with a multimeter?

Have you checked to see if any wires are shorted to ground?

Flinstigator

Shawn had power at M5 which is at the panel but did not have power at T4g which is the plug that is in the left fender that connects the parking light and left marker light to power and ground which means he probably has a break in the power line from the panel to the plug either where Stan said it was or somewhere else. Shawn you can use a meter to test continuity by connecting it to M5 at the panel and the gr/bk wire in the T4g harness to see if it's broken. You can also check the brown wires in the T4g plug to see if there is continuity between them and ground. You could also run a test wire from M5 at the panel to the bottom of fuse 28 (which should have 12V) outside of the vehicle to the T4g connector blue wire to see if the lights come on (you will have to connect the brown wires to ground since the T4g plug is disconnected. This should lock down if there is a break in the harness wire from the panel to the T4g harness. You still have an issue with your low beam headlight drivers side. Maybe a bad bulb? Maybe it's in the harness as well. That one is M3 to 56b which is a yellow/black wire to the headlight.

Shawn Stanford

Thanks for the advice everyone. I was out of town last weekend, but I'm going to be diving back in today. I'll run through the troubleshooting provided and report back.

Alan

Shawn - I have one of these that I used to identify sensor wires for a whole house alarm (with no wire labels). It worked great for that - not sure how well it would work for tracing a break inside a loom - but probably would have some usage and its cheap enough to just try.

Extech TG20 Wire Tracer and Tone Generator

Extech TG20 Wire Tracer and Tone Generator

Alan