Brake lights an issue?

[714xpress]

Recently aquired a 2010 Ram 1500 Bighorn. Last night I discovered that the third brake light works with the key off but the rear brake lights do not, with the key ON the rear brake lights work but the third brake light does not.

I've never seen this before, I also have an 03 Ram and they work in unison with the switch on or off.

Anybody else seen this before? What's the fix, without taking it to the stealership?

 

[NJMOPAR]

When I swapped in LEDs on my 3rd light it wouldn't light with the brake lights unless the key was on.
All 3 work with the truck running and that's when I want them to.

 

[714xpress]

Mine works when the key is off but doesn't work with the engine running.

 

[crash68]

Mine works when the key is off but doesn't work with the engine running.

Check if there is LEDs in the lights that don't work if the engine is running. You might need to change to ones that are CANbus friendly.