I have a 2005 4.0 4x4. With the head lights off everything works normal. However, when I turn the headlights on the brake lights stay bright as if im on the brake, including the third brake light being on. I thought about a bad switch BUT the left turn signal does not work when the headlights are on either. The arrow on the dash just lights up and stays on. Any ideas? The only thing I have done to the truck in the past year is the fog light mod a few months ago. Making it so the fogs stay on with the high beams. I'm going to try to reverse it back to stock to see if that helps. Do any of you guys have any ideas?

 

The left brake light bulb is probably shorted inside or the socket.
Also check the wires and plug for the factory trailer light harness.

 

I actually got it fixed right after I posted that. I went out and started fooling around and found the trailer harness to be shorted. All the salt and ice just corroded the crap out of it.

 

To continue on with this discussion. my issue is a little different. There may have been a backwards surge of power possibly? There is no power in 3, 4, 7, 8, 24, 28, 33.

24, 28, and 33 are "Hot at all times" connections.
24- Clutch Pedal Position (CPP) switch, Starter Interrupt Relay, Anti-Theft
28- Generic Electronic Module (GEM), Radio (Potential backward power surge? Or it never worked because it was wired direct from battery when I bought the truck.
33- Headlamps, Daytime Running Lamps (DRL) Module, Instrument Cluster

Even though the Interior fuse box has no power to 3-4-7 or 8, The head lamps and fog lamps work. I haven't checked the trailer connections up to this point.
3-Left Stop/Turn Trailer Tow Connector
4-Left Headlamp
7-Right Stop/Turn Trailer Tow Connector
8- Right Headlamp, Fog Lamp Relay

I'm trying to figure out what these fuse locations have in common to hopefully restore power again. Any thoughts?

 

Just replaced my headlamp switch, And now my switch or the back of the harness that plugs into the headlamp switch gets Hot.
Running on just the courtesy lights they are normal temp.

Any help?

Thx Bug

 

Are you running factory headlight bulbs ?

 

Yes factory all bulbs