playing with my wires


New member
Oak Harbor, WA
I was debating whether to post this here or in the electrical section, but decided it was more fitting here. I have had a few issues with my taillights that were quite boggling. my right rear blinker was inop, the brake lights with the headlights were inop, with the brakes on and the left turn signal on, the left taillight goes out completely, with both the headlights on and off. There were a couple other issues among all of this that I cant remember off the top of my head, but it was all isolated to the rear lights.

At this point I was pretty convinced that my 3 lever switch was toast and possibly my turn signal switch as well. Looking at the wiring schematic I decided to take a closer look at the turn indicator first. I grabbed my digital multimeter and checked continuity between all the pins through the various settings and found a huge amount of resistance between pin H for circuit 19A and pin E for circuit 22-160. So at this point, since I am cheap and didn't want to spend the money on new parts, I took the switch apart and cleaned up the contacts inside the switch. After I slapped it back together, resistance was at what I would consider an acceptable level, then reinstalled it. The right rear turn indicator worked like it was supposed to, so I was happy as can be.

Now for the rest of my issues. After studying the schematic, the only thing that could possible make sense is a bad ground at the left brake light assembly. It had been previously damaged before so I suspected it had something to do with it. Upon tearing it apart, I found two connections internally that were disconnected that were what makes for the chassis ground on the unit. I cleaned it all up and reconnected them, cleaned the mounting surfaces, and reinstalled. BOOM! Everything works, and all it cost me was a couple hours of my time.

At this point since I was in the electrical system, I remembered seeing some guys here doing a jumper wire mod to make their front marker lights turn on with their headlights. So back to the schematic, and I could see what people were talking about in regards to jumping circuits 491 and 21. This mod was so easy and its nice to have those marker lights on with the headlights now.

Long story short you guys, electricity really is nothing to fear on these trucks, and after spending a few minutes studying the wiring diagram, it becomes rather simple.
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