90 Burb brake lights out

I rented a Uhaul trailer Wednesday with my 90 half ton 4x4 Suburban, at the pickup all lights were functioning, 5 minutes from home the brakes dash light came on.

Now my brake lights are out and the rear passenger blinker bulb burned out. I replaced that but it only works when the headlights are out.

Any ideas where I should start looking?

Thanks,
Tom

TC90V10 said:

I rented a Uhaul trailer Wednesday with my 90 half ton 4x4 Suburban, at the pickup all lights were functioning, 5 minutes from home the brakes dash light came on.

Now my brake lights are out and the rear passenger blinker bulb burned out. I replaced that but it only works when the headlights are out.

Any ideas where I should start looking?

Thanks,
Tom

Click to expand...

That's weird. The brake warning light on the dash has nothing to do with the brake lights. There are only three switches that - if closed - will ground the brake light and cause it to illuminate (the other side of the brake light is always hot whenever the ignition switch is in any position other than OFF). The 3 switches are:

1. Brake Pressure Warning Switch - alerts the driver if hydraulic pressure is lost in either of the braking system's hydraulic circuits.

2. Parking Brake Warning Switch - no explanation needed

3. Ignition Switch - when the key is in the START position, it grounds the brake warning light and provides a lamp check function.

If you had to splice a trailer lighting harness into your rear lighting harness, I would start looking for wiring issues there. But as noted above, that would have no effect on the brake warning light in the instrument cluster.

Is the warning light still coming on when the key is moved out of the OFF position - or did it just flash on once and then never come back on?

Just curious but, are the trailer lights LED's?

Turned out the blinker bulb I replaced didn't stay tight in the socket and a 15amp fuse and all lights are functioning and the dash light went off.