Brake Lights DNF

[EchoEagle]

One of my non-computer friends has a 93 K-2500LD 5.7/4l60 EC/LB Silverado and recently his brake lights stopped working. The turn sigs work, and the 4ways work, fuses good. First, he replaced the brake pedal switch. Second, I cleaned the rear ground and deleted the rear trailer harness; no effect. I read a couple other threads on this topic and am sure it's the Brake Lamp Relay.(if it has one) Problem there is; I can't find the sucker. My own truck, for example, which is only a year newer, has a relay on the firewall, above the terminal block, beside the brake booster.(However, the actual brake switch is different, mine white/his black.) On this 93 gasser, there is the cruise module there, and I cannot find a b/l relay anywhere else in the engine compartment, or under the dash. There is a brake controller, a nice porportional one. (can't remember the brand, but it appears to be a professional install). Next, I guess I should dig deeper into the harness where the controller is? I don't really know... Could it be the signal-stat?

 

[ak diesel driver]

check the circut board in the taillights

 

[EchoEagle]

thanks ak. I will try switching both taillight units with mine..

 

[EchoEagle]

alright!!!!! I found the solution! I found the correct wiring diagram today. This truck does not use a relay for the brake lights. It was a bad trailer that caused it. The white wire is the output from the Brake Pedal Switch. It goes directly to the signal-stat plug on the lower portion of the steering column. This 14ga wire had burnt off on the signal-stat side of the harness coupling, right where the insulation ends, and the wire goes into the coupling. Some other wires there were a little green also.. sorry no pics. Replaced the signal-stat; problem solved.

Don't use over-rated fuses!
If your trailer is blowing your fuses try booster cables or a clip jumper to establish good ground from the truck to trailer.