No brake lights when engine running

[HotWheelsBurban]

The third brake light will work if the turn signal switch is bad. Had this happen on my Burb in October 2018, a couple days after coming home from a swap meet trip to Louisiana. The turn signal s quit working, then the brake light part of the taillights. But the third light still worked.
Replaced the multi function switch and everything worked like it's supposed to!
The third light gets its power and activation from a circuit that doesn't run through the multi function switch.

 

[Erik the Awful]

I stand corrected.

 

[HotWheelsBurban]

I stand corrected.

Maybe it's just the 95 up trucks and SUVs, since didn't the early ones not have a third brake light? That would definitely account for a wiring difference! Just recounting my personal experience with my Burbs, and I have none with the early models.

 

[GoToGuy]

My 93 has just cargo light. And the 95 has the cargo brake light combo. Which I upgraded to a led white and red combo.and is much brighter cargo and red led brake.

 

[mockspeed88]

So the turn signal switch did not fix it. I'm perplexed. Only when the truck is running I have no brake lights.

 

[mockspeed88]

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[mockspeed88]

So I'm looking around online and someone else had this issue. Seems like it was a front of engine ground? Where is this located on my 94?

 

[Erin]

So I'm looking around online and someone else had this issue. Seems like it was a front of engine ground? Where is this located on my 94?

Mine is somewhere below the AC compressor.

 

[thinger2]

I have a 94 k2500. I recently installed a transmission. I do not have brake lights when the motor is running. Everything else works

Its bad grounds and the brake light switch.
Shes a bit crusty bud.
You need to repair all of the bad contacts and grounds ..
And get a new brake light switch.

 

[GoToGuy]

Did you read the earlier threads? If you have bad or no grounds, then how do you have turn signals operating and brake lights with key off? As i said earlier something about turning the key. As proven by testing, he has turn and brake lights until the key is moved. Has anyone looked at the wiring diagram? Good practice on changing the turn switch. Try this.- insert ignition key. Turn key to first click notch not quite to run position. Test brake lights. Yes or no? Turn key to next position, run. Brake lights- yes or no? Thats it i tryed...