Join Date: Sep 2000
Location: Shrewsbury, MA, USA
On my 96 Jimmy the High mounted stop lamp is directly powered from the load side of the brake switch, some cars and GM pickups have a relay that operates the high brake lamp. I think this relay is what causes that slight difference between when the brake lamps come on and when the high brake lamp comes on.
The normal brake lamps are powered from a parallel circuit that goes through the emergency flasher switch AND the blinker circuit. There is a contact in the emergency flasher switch that is normally closed that allows power from the brake switch to pass through it to the two rear blinker switch contacts in the blinker switch. As long as the blinker is in the center position, power passes straight through these two contacts (left and right)in the blinker switch and on to the brake light filaments.
There is a separate feed from the fuse panel for the blinker circuit that also feeds the blinker switch, that also comes thru the emergency flasher switch. The blinker circuit to the rear lamps are fed thru a different set of contacts in the blinker switch (mine has seven sets-front left and right, rear left and right, two brake lamp feedthrus, and one spare). The two sets of contacts for the brake light filaments join back together after the blinker switch, so if you rear blinkers are working, but the brakes aren't it looks like the problem is in the emergency flacher switch.
If you have the same type of setup maybe the contact in the emergency flasher that feeds thru to the brake lights is stuck open. Did you use it recently? Try to cycle it on and off a few times to see if you can free it up.
1969 Indy Pace Car
350/300HP RPO Z11
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