Another dumb electrical problem...

This morning I went to head out for work and I noted that all 4 bulbs were lit up when I had my lights on, normally there would just be 2 lights on (parking lights) in the back. So I jumped in, pressed the brake pedal down and noticed that they did NOT get brighter... The third brake light works fine - and turn signals work fine too.... why not the tail end brake lights?

Relay? Fuse? FCM? brake switch?

recap

1) 3rd brake works as normal
2) brake lights stay lit when truck is on, and lights are on

any ideas???

 

update...

Ok, the other night I pulled all my relays, and my fuses for my tail lights, tow lights, ect... and my brake lights started to work fine.

This morning I get in my truck, click the key to the "on" position and I heard a click from behind my gauges.... I looked in my mirror and noticed that my brake lights were on. I turned the key off, and then to the "on" position once again and the brake lights were on and I heard the same clicking noise.

I started the truck and shut it off a few times to see if that would "cycle" the problem and sure enough it fixed it. But once I got to work I saw that my brake lights were all on again (except the 3rd one on the back of the cab)

So I turned the truck off and pushed the brake pedal down and I heard that same click noise from behind the gauges again, I looked in my rear view and saw my brakes lights on (reflection from the building windows) then I clicked the ignition to "on" again, heard the click and saw the lights on again.... I started the truck and the lights went off, then they flickered a few times came on, then flickered and went off.... each time they flicked I heard the clicking sound from the dashboard!!!

what would make this do this?

 

OK, from doing a little reading, it seems that the FCM controls the brake lights, but NOT the 3rd brake light, that is controlled by the brake switch itself.

So how much does a FCM run? how about labor?

 

Did you ever get this fixed? What was it?
What year is your truck?

 

Mine did that but it ended up being the trailer brake controller inside the cab went bad..
kept the brake lights on when the truck was running.. Replaced the trailer brake and problem went away