Trailer Tow Relay

bedwards97 · March 19, 2006

Does anyone know how the trailer tow relay on 99-02 Sierra is wired? Or, does anyone have an internet link with this info?

The relay is located under the driver side dash, next to the steering column. I want to be sure I've connected the wires from the brake controller to the Tekonsha harness correctly.

Initially I connected the wires by their color (red, black, white, blue) but I don't believe this is correct, since the red indicator on my brake controller remains lit even when no brakes are applied.

Cranky1 · March 20, 2006

Does anyone know how the trailer tow relay on 99-02 Sierra is wired? Or, does anyone have an internet link with this info?

The relay is located under the driver side dash, next to the steering column. I want to be sure I've connected the wires from the brake controller to the Tekonsha harness correctly.

Initially I connected the wires by their color (red, black, white, blue) but I don't believe this is correct, since the red indicator on my brake controller remains lit even when no brakes are applied.

<{POST_SNAPBACK}>

If I remeber correctly, my mechanic warned me about using the factory harness, the white wire from the brake controller is a ground wire, the black wire is the power wire as with any trailer wiring. If the harness is the one from GM that was in your glove box, black is ground and red is positive. I would use a test light to be sure. The blue wire should be to your trailer brakes, the red wire is to the brake light switch (hard wired) if you didn't have a harness.

I bought the Reese brake controller harness kit and all the wires connected by the identical color. I then plugged it into the port, top row, 2nd from the left. Works great...

Also, you will have to go to the fuse center under the hood and put in a fuse for the brake controller. If you want a hot power feed to the trailer, there is a second fuse.

If you are not plugged into your trailer, your brake controller should not have any lights lit up. Could you have the adjustment dial cranked up? Did your controller come with the mercury switch and the controller has to be perfectly level?

I hope I haven't confused you more

kdm101 · March 20, 2006

If I recall, the manual for my controller (Tekonsha Envoy) came with a sheet that had the color codes for the big 3 so you could match the appropriate wire to the factory harness. My factory harness did have a tag on each lead though so the extra instructions weren't really necessary.

From those instructions, the color of the wires are:

stoplight = red

ground = white

power source = black

trailer brake power = blue

Just match those up to the appropriate leads on your controller. My envoy's wiring wasn't the same colors, so it looked really strange once I was done. This is, of course, assuming you have the trailer towing option installed, otherwise, the black and blue connections won't be present and those wires will have to be run by you.

campertime · March 20, 2006

This May HELP

builderpaul · March 20, 2006

If you are not plugged into your trailer, your brake controller should not have any lights lit up. Could you have the adjustment dial cranked up? Did your controller come with the mercury switch and the controller has to be perfectly level?

This is not true with the Prodogy controllers. There will be 1 or 2 lights lit (depending on your gain setting) Even without the trailer hooked up. These lights will stay on for 10 min with no brake activity, then go out till you step on the brake again. This leads many to think they are on all the time. If you look back after being parked for 15 min you will see the lights are out.