So I've noticed that the high mount third brake light doesn't come on when im actually hitting the brakes, headlights on or off. Upon driving home yesterday, I made sure to notice other trucks. It seems that the vast majority of trucks don't have theirs working. Is it supposed to work at all times? Only when the headlights are on? I don't want to try and replace the bulb because I used some Ultra Black to seal it from leaking. Last time I tried to remove it, it was a biotch. Let me know.
Thanks!

 

Third brake light is supposed to come on every single time the brakes are applied. It is a brake light. Does matter if the headlights are on or off. I would check the bulb. It's probably burned out

 

Definitely should be working because your cruise control is tied to it. Most likely the bulb

 

Dang it...sounds like I'll have to break that seal :/

 

You won't be breaking anything. It's just basically a piece of foam weather stripping.

 

I used Ultra Black when I sealed it to prevent leaking

 

You should have let it fully dry, then put it on.

 

can you please elaborate on this?

 

Yeah....shoulda, coulda, woulda....

 

The third brake light circuit is used to tell your cruise control when you apply the brakes, so it doesn't try to cruise through your braking. If the circuit is dead somewhere, cruise won't work at all.