I know this isn't a diesel specific problem but here goes...

I turn on the running lights and the brake lights come on. Checked the bulbs and removed all and still the high mount brake light comes on... Disconnect the brake switch and still... The turn signal switch will stop the problem but it would be difficult to drive that way. I did change the ts switch (used - no history) and no difference.

Any ideas? I did change the headlight doors/trim this weekend but what could I have done? Just unplug and re-plug wires. And there is no brake light circuit up front that I could've shorted. Out and back in with the batts.

I am stumped.

 

When you hit the brakes do they go out???Is your 3rd brake light on also??(check that bulb too)It may sound stupid but the bulbs in the tails might need to be pulled and flipped over in the plug.Do you have a test light?

 

These may help,sorry they are a little big...thanks to TJ for these

Webshots-Grand Wiring Dia1

Webshots-Grand Wiring Dia2

 

Check the grounds by the head lights??

 

Remove both outer (bedside) stop/tail/turn bulbs, and turn on the parking lights again. If the center stop light no longer lights up, there's an internal short in one of those bulbs (the two filaments touching, for example). Try putting each one back in and check to see when the problem comes back.

 

iv done what ron described before, there not suppose to be able to go in eather way, but you can do it without realizing it