Brake/ parking light issue

[Haybag]

Have an electrical issue on my 72 k20. When I press brake pedal the left front marker light comes on along with the brake lights. I figure it is a ground issue, but have checked and cleaned taillight grounds and added a bed to frame ground with no change. All other lights work normally except when you press the brake, then the driver side flasher won't work. Any ideas?

[lutronjim]

Possibly turn signal switch. I had some weird problems with mine - sprayed liberally with contact cleaner/de ox and it cleared up

[VetteVet]

Sounds like the front parking turn light pin and the left rear brake pin are touching in the turn signal switch.
I would pull the left front turn light wire,( light blue), in the column connector, and step on the brake. It should not do it with the key off either because the signal lights shouldn't get power without key power like the brake lights do.

[Haybag]

Well, did some more digging and found the problem is in the column. By wiggling the knob for the hazard flashers I can make the light go on or off, so something is rubbing and shorting in there Also the 4 way flashers don't work at all, but probably related to the same problem, guess I will have to get into the column.

[67C10Step]

When I went through the wiring on my 67 I got the battery from my old lawn mower and set up some test wiring. I unplugged the turn signal switch and, using the wiring diagram, verified and corrected anything wiring wise on the truck first. That way it eliminated the switch from the process so when I plugged the switch back in if I had issues I knew where they were originating.