Help No brake lights

You said this was after you had the truck washed, if they used presure washers look for wires that may have.been blown off under the hood I seen that once at a wash in elk grove california.

 

Maxi/mega fuse under hood.

 

Can't recall exactly, usually black cover marked fuse.

 

It's wise to carry a cheap probe type tester. A fuse can be bad and look ok. It's also quicker.

 

Usually at a truck wash they will cause a water short under the hood if you have a problem harness connector. Or someone careless with the brush will smack the pigtail washing the back. The pigtail connections are very close together with strand wire. It's common for screw to back off and a connection loose. Smacking it with a brush could of caused a short.

My first though would be a blown fuse. My second thought would be one of the relays with wore out contacts. The short was enough to finish it off.

Normally they would hook the laptop up and check all your switches that way. The circuit runs through many things. Once you are convinced you found the right fuse. You can check the brake light relay by swapping with a like one in the panel. The relay panel is on the firewall under the hood if not mistaken.

Like others said, Once you are convinced you found the right fuse, then put a tester to your brake switch and see if you have power coming to it. Then with the pedal pushed in make sure power is coming out. It could of coincidently went bad.

Once you fix it, I would check it out with the trailer pigtail disconnected. Then if it blows again afterwards, you know the pigtail is shorted.

I had my APU AC quit working one time. Turned out it was the truck wash smacked the condensor fan wires with the brush and messed it up. Them guys don't think about them things.

 

Some trucks Pete 387 will not have lights if the front blinker light is out...but most likely a fuse