I bought an aftermarket GM tilt column and I wired my F100 with a GM style aftermarket harness. I see in the way GM did things, that they sent brake light power through the column. But I'm using a hydraulic brake switch, not a pedal switch. So I didn't send power to the column and just wired the brake lights direct. Fast Forward to me trying to get the lights all working. If I do not connect the brake light wires to the the rear turning signals, all four corners work correctly. As soon as I connect the brake lights, the front turn signals work fine, but both rears flash at the same time. Plus I get some weird versions of one brake light working and 1 turn signal at the same time or just all brake lights and the flassher stops. Could there be some link between the turn signal switch and not having brake light power going through it? I've wasted 3 evenings trying to figure this out.
Go back and read the wireing diagram for the G.M. signal switch. The power from switch MUST go to signal switch, it don't know the difference weather it's in a Ford or some kind of G.M. unit. They both use the same routing through sig switch. It's just different colors of wires.
I'll add power goes direct from Batt + to switch then to signal switch wires and out to brake lights. There is a front light system as well as a seperate rear Brake/ Sig lights.
The GM turn signal switch has brake light switch power going to it, this gets sent to the rear turn/brake lights on each side. I don't know how you wired your rear lights...is there a separate bulb for the brake lights, and for the turn signals? Or did you connect the brake light switch to both sides, and also connect the turn signal wires to a single bulb on each side? btw it does not matter if it's a pressure switch or a mechanical brake pedal switch, they are both wired exactly the same way. So this statement does not make any sense to me:
the brake light wire has to run through the turn signal switch if you are using one filament for the brake and turn. the turn signal switch will shut off the brake to the side signaling so it can flash.
Also if you have bad grounds to your lights all sorts of strange things will happen with the lights. So you cannot test them while hanging by the wires, as the housing needs to be grounded.
Give us the number of signal wires and colors of each and I can tell you what each of the wires are supposed to go to. Also does the switch have 4-way's as part of it?
A brake light switch is a brake light switch (generally speaking). Whether pressure switch on a brake line or a mechanical switch on your pedal, they both manage the brake/turn circuit the same way. Get a GM column schematic and wire your switch accordingly.
What harness kit are you using? I'm running a Ford column (1959) and the Kwik Wire kit, I had them give me a GM column plug set with the GM harness kit. I run a hydraulic BL switch to a proportioning block. Look at the Kwik Wire harness book, start with page 35 and see if it helps. https://kwikwire.com/content/kwik-wire-instructions.pdf
I just saw this. Like my post below says, I am using a hydraulic BL switch and went right along with what the harness-maker said, followed the GM code, had to translate over to the Ford column code. I left some extra on the wires going out to the switch in case I went to one on the pedal down the road.
The only way you can keep brake power out of the column is like some imports and use separate bulbs for brake and turn signals or use diodes
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