F350

[jrex7]

The break lights on my F350 super duty are not turning on when I apply the breaks. I already looked at the fuse box and all the fuses are ok, including the break fuse.

Any ideas as to where should continue looking?

[97chevyman]

check the little sensor on the brake pedel. Try taking it out and seeing if the brake lights come on, you might need a new sensor.

[jrex7]

Originally Posted by 97chevyman

check the little sensor on the brake pedel. Try taking it out and seeing if the brake lights come on, you might need a new sensor.

I already checked that. I measured power on the cables coing to that switch and there is power. I disconnected the brake switch and used a wire jumper to by-pass the switch and feed power directly to the breaks but they still don't go on.
By the way, my rear lights dont go on at all even when I turn on my headlights or when I apply the hazard lights.
My head lights do turn on and front hazard lights flash normal.

Any more suggestions are appreciated.

[FreddieJB86]

check the bulbs?

[97chevyman]

Check the body grounds.

[ModMech]

There are two connectors thast would cause this. Depending on the MY, one is either below tha master cylinder and inboard, or next to the transmission, the other is behind the rear axle. If these get corroded, you'll not get brake lights.

Oh, another thought. Do your turn signals work OK? If so, you need a new turn signal switch, and forget that wiring stuff I asked about.

[jrex7]

Thank you all --

ModMech. You were right. A few days ago I was trouble shooting a problem with my truck not turning on after presurewashing the engine. That problem turned out to be a relay that went bad after getting wet. But on the process of troubleshooting that problem I seem to have disconnected the connector you mentioned right around the master cylinder. Now I have lights and the breaks are functioning just right.