Hazards feeding on to brake lights

As others have said I think it is a ground problem... Possibly a short to ground, that is back feeding through the brake lights.

We had this kind of problem all the time when I worked in the fertilizer industry. I finally got sick of chasing down electrical problems that 90% of the time where related to bad grounds. Thats when I went through and double grounded every single light... Each light grounded through the normal ground wire, and additionally I added a short pigtail that spliced to that ground wire right at the light and the other end was screwed or bolted directly to the chassis less than 6 inches from the light. Doing this eliminated close to 70% or 80% of the problems we were having with trailer lights.

With you problem... I would disconnect the normal ground from the brake lights. Then use a jumper wire to temporarily give the brake light a ground directly to the chassis. If this fixes the problem you know it is a grounding problem.

 

I’ve had many vehicles that just worked that way. So unless it use to work independently then there’s nothing to fix.

 

Here's some info. It may or may not be what you're after.

 

Haha I just found my info.
Same as yours.....
If he does that it will cure the problem.

 

Nice!