Chevy & GMC Vans

If you have or want trailer wiring on your vehicle then the wiring colors & what they are for are:
Large white wire is ground.
Small white wire or light blue is high mount brake light. (dependent on year of vehicle)
Small brown wire is the marker / clearance / park lights.
Small yellow wire is left turn signal / brake lamp.
Small dark green wire is right turn signal / brake lamp.
Small light green wire is back up/reverse lights.
Large orange wire is battery feed wire.
Large dark blue is the electric brake control wire.

If you have a factory tow package, the factory wires will be bundled in the right rear of the van in the jack storage area.
The other ends of the orange & dark blue wires will be tucked under the carpet in the left front of the vehicle. Like in this pic.
The orange wire (dependant on year) will have a connector on it that will plug into the fuse block.
The dark blue wire will need to be connected to the brake controller output wire.

If you do not have a factory tow package, the wire colors are still the same as above for the lights. You will need to access the wiring at the rear of the vehicle & tap into them for the lights. There is unfortunately, no quick connect plug in that can be used on these vans. The power can be taken off of the 'A' & 'B' power studs in the underhood fuse box to power up the brake controller & the battery feed to the trailer. These studs are fused thru 30 amp maxi fuses.

Brake controller wires are as follows:
The white of the controller gets connected to ground.
The red wire of the controller gets connected to the white wire at the brake pedal switch.
The black wire of the controller gets connected to a fused battery power source. (Stud 'A' or 'B' in the underhood fuse box - '96 & newer)
The blue wire of the controller gets connected to the blue from under the carpet.

6 and 7 pin connector configurations

Thanks for that James. I have a flat plug wired in for mine right now, but if we ever go to a larger trailer or decide to borrow my Parent in laws travel trailer I will need to rewire and get a brake controler. This will help a lot.

Don't know how I missed these two posts but anyways, Nice posts James and Tristan, this is exactly the kind information we are lookin to archive in our forums.

[quote="v8famvan"]If you have a factory tow package, the factory wires will be bundled in the right rear of the van in the jack storage area.
The other ends of the orange & dark blue wires will be tucked under the carpet in the left front of the vehicle.
The orange wire (dependant on year) will have a connector on it that will plug into the fuse block.

Thanks for this info James, Saves a lot of time on everyone. Can you show a picture and break down of this connector block? I think they changed a couple of times through out the years. I've been meaning to ask you to do this for a few weeks now.

v8famvan wrote:If you have a factory tow package, the factory wires will be bundled in the right rear of the van in the jack storage area.
The other ends of the orange & dark blue wires will be tucked under the carpet in the left front of the vehicle.
The orange wire (dependant on year) will have a connector on it that will plug into the fuse block.

Thanks for this info James, Saves a lot of time on everyone. Can you show a picture and break down of this connector block? I think they changed a couple of times through out the years. I've been meaning to ask you to do this for a few weeks now.

I added a how-to here for how I wired up my 2003 Astro with a 7 pin trailer plug.

Good write up!
Remember too, occassionally there is light green wire used for a backup light. My flatbed is wired for a back up light instead of the aux power. I get the luck of having 3 trailer, every one with a different connector wired differently ](*,)

I wired in the back-up lights. The 7 pin configuration has provisions for the BU lights.

v8famvan wrote: If you do not have a factory tow package, the wire colors are still the same as above for the lights. You will need to access the wiring at the rear of the vehicle & tap into them for the lights. There is unfortunately, no quick connect plug in that can be used on these vans. The power can be taken off of the 'A' & 'B' power studs in the underhood fuse box to power up the brake controller & the battery feed to the trailer. These studs are fused thru 30 amp maxi fuses.

Does that mean the wires (Orange and Dark Blue) are not there is there is not a towing package? Or, are they there but not hooked up?

I have a headache, so I may not be seeing what is right in front of me, but I have looked and can't find the brake control or charge wire. A bigger pic would be helpful.

LiftedAWDAstro wrote:I added a how-to here for how I wired up my 2003 Astro with a 7 pin trailer plug.

Where is the How To?

If you don't have the tow package, you most likely do not have the Orange and Blue wires.

The how-to was in the tech gallery I think...seems to be gone. It may be in the towing section though.

LiftedAWDAstro wrote:If you don't have the tow package, you most likely do not have the Orange and Blue wires.

The how-to was in the tech gallery I think...seems to be gone. It may be in the towing section though.

Since they are likely not there, where is the best place to run them when putting them in?

I ran them inside the van where the tail light harness runs. This involves pulling trim pieces inside. Takes a lot more time but it is done right. Another option is to run the wires along underneath.

I chose to run them underneath as I did not have the time to pull panels, and my past experience when I do pull them is I tend to break things. Having said that I ran into one problem of where to run the wires through the firewall to hook up to the brake controller. Right now they are running around the edge where the dog house mounts up, but that leaves a gap which I don't like.

So where can I run the wiring through?