brake lights inoperative

[petedogg]

Hello,

My ’92 SHO has been having some electrical issues lately. My rear brake lights did not turn on when I was braking a couple of weeks ago, so I changed the stoplight switch on the brake pedal, and all was good. Now, they are not working again, and I no longer have power at the switch for the brake pedal. I checked the fuses, and all have power running through them. I also noticed that my hazard lights, fog lights, and flash-to-pass feature of the high-beams do not work. The headlights (including regular high-beams), tail-lights, and turn signals work fine.

I looked at the Helm’s, and it appears there is nothing between the fuse panel and the brake pedal switch, is this correct? Could it be a short in the wiring? Based on the parts that are not working, it sounds like a multi-function switch issue, but it doesn’t seem like it would control power to the brake pedal switch, or does it?

Thanks in advance.

Peter Wagoner

 

[Troglodyte]

Power for the brake lights also go through the MFS.

 

[petedogg]

I just tried putting a new MFS on, and I still have the same problem. No brake lights, hazard lights, ect (as mentioned above). An interesting thing to note is that my speakers for the radio went dead around the same time (or possibly at the exact same time) as the brake lights problem. My radio has power, and shows the station on the display, just no output out of the speakers. It's weird. I think I have some electrical gremlin . Does anyone know where the ground is for any of these circuits? Anyone have an EVTM or can chime in for some ideas of where I can start to troubleshoot? Thanks.

 

[SHOZ123]

The wire diagrams are in the "How Do I" forum.

 

[93blueSHO]

I just bought a SHO with the same problem. I too was looking at the wiring diagram on a rainy night. my wife looks out the window and ta da my hazards are blinking away.i go out there and found it to be the hazard switch itsself. i originally had no brake lights(except the led's in the wing)/no turn signals/no hazzards. By pushing or pulling the switch in different directions i could get the brake lights/signals/hazzards working. maybe the switch somehow got corroded or something. hope this helps before you spend more money chassing a goose!!!!

 

[93blueSHO]

oh yeah the diagrams i was looking at didnt seem to show the hazzard switch at all. but it seems the power passes through it before going to the rest of the cicuits thats why you lose all the fuctions brake/hazzard/signal if the switch is bad.
as for the speakers? im not sure if all SHO's have one, but there seems to be some sort of amplifier screwed to the back of the back seat in the trunk. maybe it lost power, or went bad.

 

[93SHO'nOFF]

I know you said that this looks ok but check the wires on the connector at the brake light switch on the pedal. The wire breaks off where the crimp is under the cover. If wires look ok see if you have power to the switch and through the switch when depressed with a test light. I've seen some that the wire looks ok but it is broke inside the wire casing.

 

[petedogg]

I actually had to take the car into the shop to find the problem. I had no time, and it needed to be fixed fast, since it was a safety issue. It took them 3 hours to find it; it was acually a corroded (and broken) wire up close to the airbox. This really suprised me. I really did not think it would be way up there, since my problem was somewhere between the fuse panel and the brake pedal switch. It actually appeared from the outside to be OK, but it was broken. I still need to look for the exact location of it, but it did fix all my problems, including the output from the speakers. Unless I'm just wiring diagram illiterate, I saw nothing that included brake lights, hazard lights, high beam flash, fog lights, AND the speaker output all on one circuit (but not turn signals and headlamps+taillights!). My only guess is that it was a ground wire or something. That would seem to make more sense to me.