No brake lights.

Reply Subscribe

Thread Tools

Search this Thread

Feb 1, 2026 | 11:45 AM

#31

BareBonesXL

Fleet Mechanic

Joined: Jun 2023

Posts: 1,394

Likes: 384

From: WA

You seem to be saying that a short circuit in the wiring between the multifunction switch (MFS) and the brake light itself would not blow the fuse because the power comes through the MFS. Why would this be the case? Current is current. There's no protection in the MFS. There's no fuse shown anywhere in the diagrams, (01, 02 and 03), except at the power source.

Fuse > D-D > MFS > A-A and B-B

Feb 1, 2026 | 01:00 PM

#32

projectSHO89

Hotshot

Joined: Jan 2004

Posts: 19,768

Likes: 1,082

From: St Louis

Quote:

Originally Posted by BareBonesXL

My point is that since the rear stop/turn lights work correctly in hazards or turn signals, they are not the location of the short circuit. If there was a short in that portion of the wiring, either of the fuses supplying power to the flasher relay would have blown. That isn't happening so that portion of the circuit is okay.

The short is between the brake light switch and the MFS. Basically, it could be anything at or after splice S291.

Feb 1, 2026 | 01:48 PM

#33

manicmechanic007

Hotshot

Joined: Jul 2020

Posts: 10,575

Likes: 2,678

From: Near Salt Lake City

Brake lamps have been running through the turns signal switch since the beginning of time
The old classic symptom of a shorted turn signal switch was to hit the brake and have one of the front turn signals light up

Feb 1, 2026 | 01:52 PM

#34

BareBonesXL

Fleet Mechanic

Joined: Jun 2023

Posts: 1,394

Likes: 384

From: WA

Quote:

Originally Posted by Ben76251

All other lights working. Ie. Hazards, reverse lights, running lights...

Quote:

Originally Posted by projectSHO89

My point is that since the rear stop/turn lights work correctly in hazards or turn signals, they are not the location of the short circuit.

I see. I didn't know that the hazards could be used to test the wiring past the MFS. I took a harder look at your MFS diagram and see it now. (Ironic, but your red arows got in the way).

So, if the OP can find the connector, C253 or 258, for the 511 / LG wire and disconnect it he can narrow things down to the MFS itself or the wires on the way to the MFS. I assume that LG means light green. Looks like it plugs directly in to the MFS at C258, or along the way at C253. There are also other wires at C253 that might help identify it. Look for C253 on the diagram.

Seems like the next thing to do. Unplug from MFS, insert fuse, press brake pedal.