Trailer Brake Controllers on 1999 and Older GM Pickups
"Standard" Wire Colors from Ford Trucks
When using a wiring harness supplied by your vehicle’s Manufacturer (OE Harness), DO NOT MATCH COLORS.
Please follow wiring chart below.
- Ford Wiring
- Brake Controller Wiring
- +12 Volts
- Ligth Green
- Stop Ligth
- Dark Blue
- Trailer Brakes
Remember, the above colors are just a GUIDE. your colors may be different, read the instructions!
I took a couple of pictures of a 1999 Chevy with the tow package. On GM trucks 1999 and Older, The "tow package" in these trucks amounts to installing the plug on the back of the truck, and running two wires up from the plug to the fuse box area. It's up to you to do the rest...
First, find those two wires. One is Red/Orange, that is the Aux power to the trailer plug (operates Cargo Trailer lights, charges batteries, etc.). The other wire is Blue, and is the trailer brake wire. They are inside the harness somewhere. On this truck, they were under the brake booster...
Connect the red Wire to the Stud on your fuse box, you will have to buy a metric nut, not sure of the size, to bolt it to the stud, and put a fuse in the slot that powers the stud (30 amp). In addition, attach a second wire to the stud, long enough to go through the firewall and reach the brake controller. The will Provide the 12 volt power for your brake controller. You will hook this wire to the Black wire on the Tekonsha Control.
Next, with a wire connector, extend the blue wire a few feet so it will reach the dash. You will hook this to the Blue Wire on your brake control.
Under the dash, find a spot and drill a small 3/8" hole in the fire wall, or find a rubber grommet, and cut a small hole in it. Route the wire through the firewall. If you drilled a hole, fill the hole with Silicone after finished to seal and prevent the wires from getting cut. Route the wires away from any moving parts (brake pedal, steering column)
MOST (not all) GM truck will provide a terminal in the box under the dash that provides the brake light signal (It lights up a test light when you step on the brake pedal). Using a test light, find that terminal, and confirm it does not flash with the turn signals. With a standard spade connector, hook the red wire from the Tekonsha Controller to the connection.
If you can find this terminal (not all trucks have it) then it is Bad News....Then you have to find the brake light switch. It is WAAAAY up there. With your test light, find the wire that lights with the brake pedal when pressed. With a side tap (scotch lock) tap into that wire. I have located the wire before, just by probing with the test light as various connectors until I found it from memory, and White Wire is what you are looking for....