Multiple electrical issues

Good evening,

Yes, there are grounds back at the tail lights on the cab.

Make sure there are good, clean and tight.

https://www.2carpros.com/articles/how-to-check-wiring

the flickering could be the alternator not working correctly.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Check the voltage at the battery with the engine running. it should be 14 to 14.5 volts.

Roy

Thank you Roy! Now the dash lights went out. I had this flickering before and I cleaned both negative connections. The one on the front of the engine and the second one on the core support. That stopped the flickering for about six months. The grounds for the tail lights are where? Are they under the bed area or do they travel down the wire harness and ground up front?

The grounds are at the back by the tail lights. they are bolted to the body.

I attached a picture of the location for you to view. It is on the frame rail at the rear of the truck.



Roy

Okay, cleaned the ground wires and they all work correctly. But the high mounted brake light stopped working. First I checked the bulbs and they were good but I am not getting no power back to the light itself. I checked the vechmsl fuse and it was blown. Replaced fuse and it still didn't work. Checked power at that fuse and it is working. Where do I go next? I guess the wire comes out of the fuse box and goes through the door sill and up the third door rear door panel.

You have a relay for the third light in the fuse block.

Check both fuses listed in the diagram I sent you.

use a test light to check on both sides. Yes, they run the wire under the plate on the drivers side.

Roy

Both fuses have power when I push the brake pedal. I pulled the relay and switched it with another and nothing. When I installed the relay I can hear it click so I think it is working. I guess the power comes from the relay and goes to the light.

If the relay clicks, then it is engaging the load. that indicates a wiring issue between the relay and the light itself.

Roy

The wires run up the "A" pillar and above the headliner. There are four wires; orange, blue, black, and white. I don't have a schematic for this truck but I did drop the interior dome light to see a black and yellow wire hooked up to the brake light. I don't see a yellow wire down stream above the headliner.

The schematic was attached in a previous post. The blue and black are the wires.

What messed me up was the four wires go way back in the headliner into a plug and the blue wire turns into a yellow color wire. I don't understand why they use this thin wire to start with and then after the plug it steps up to a larger gauge. All the wires look like they have been a little warm at some time. I guess it is cut and replace time. Thanks for your help Roy!

You are welcome.

Always glad to help.

Roy