[schnitz]

I have a buddy who is working on his son's '96 GMC Jimmy. The problem is that the third brake light comes on, but neither the left or the right does. He says that there is no corrosion in the bulb sockets (he checked that right away), and the fuses all appear to be good. I told him that the trailer wiring is one possible reason for the problem, but I'd prefer a second opinion. Got any thoughts?



In a while, Chet.

[hotrodlovr]

maybe the stoplight switch? although i dont see why the third light would still work if it was the stoplight switch... there not very expensive, i'd honestly try that.

[ChevelleSS_LS6]

check the bulbs themselves, continuity tester?

do the blinkers work?

edit: do trailer brake lights work, do trailer blinkers work?

[302 Z28]

The brake light switch is the first item after the orange wire leaves the fuse. From the brake light switch the white wire feeds the cruise control module, the electronic brake control module, the turn signal switch. The rear stop lamps are fed through the turn signal switch. The third brake light is fed directly from the stop light switch.

If you have other lights working at the rear of the vehicle that pretty much eliminates any ground problem, except those created by faulty trailer wiring. My guess would be a faulty turn signal switch.

Update: When the hazard flasher switch is engaged the path to the rear stop lights is by-passed. Is perhaps the hazard switch engaged and the hazard flasher is not working? If not, engage the hazard switch and see if the rear stop lamps flash. If they do, then it is not a wiring problem to the rear and that pretty much points to the turn signal switch.


Vince

[schnitz]

Thanks for the help guys, especially vince. I need to have my wife run off a print copy of those schematics. I'll also call Fred and ask about what all presently works and what doesn't. Once I find that out, I'll post and keep you guys informed. Thanks again.

In a while, Chet.

[302 Z28]

Glad to help, let us know what you guys find.

Vince