I have an 86 Chevy truck, the left brake light will not come on. All other lights work fine, running lights, flashers, and turn signal. I have change brake light switch and bulbs. I even cut a harness out of another 86 and spliced it in from the cab back thinking I had a short, but ended up with the exact same thing....no left brake light. Any ideas from anyone ?

 

Socket is not grounded?

 

Socket on the old and new harness grounded..that was 1st thing I looked at on each.

 

This truck has a brake light switch and a cruise control switch mounted next to each other on the pedel. BL switch has been replaced any chance the CC switch might have something to do with it?

 

The socket may be grounded, but make sure the contacts in the socket are making good connection with the bulb. Test the contacts in the socket with a meter and see if it is getting 12 volts while someone is pushing on the brake pedal.