CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Hitch wire colors & what do they do

I need to hard wire a 7 prong towing hook-up back into my 07 Silverado classic. The guy I bought this from had sold the stock hitch but did not tell me he cut off the the stock prewired plug. I figured out what the five 16ga wires are and what they do but there are also three 10ga wires: red,black and dark blue. I need to find out what these are for. A second question. Why on the 7 prong plug I am trying to wire in is there no where to slice the actual brake light wire? Thanks for any help you can give.

Well, I can answer part of that. You don’t have just one “brake” wire because the right and left brake lights double as turn signals. So when you hit the brakes, it turns on your left and right turn signals (just not blinking). When you turn on the signal, it flashes the brake light on whatever side you’ve selected.

A 7-prong hitch connector is for an electric brake controller system on the trailer. Three of the wires, most likely the 10 ga., are for the electric brakes. Use a multimeter, and double-check these wire connections.

http://www.marksrv.com/wiring.htm

I understand what you are saying. The only reason I asked is in the vehicle wiring there is a dedicated wire for the brake lights.

The dedicated brake wire is probably for the high mounted brake light on your Silverado. Trailers don’t have a high mount light and so use only the signals for the left and right brake lamp / turn signals.

That is pretty much what I was thinking but, I did not want to assume I had it right and ness somthing up. That link is awsome. It is the best I have seen and I have looked at alot. In one section it mentioned I might need a converter for the dedicated brake light wire. Any idea what that is or where I would find it? Thanks a bunch.

That makes sense. Have you looked at the link BustedKnuckles attached. Good stuff. In there it says some GM hook-ups need a converter. Any idea what that is?

The converter is required if the turn signal lights are separate from the brake lights on your truck. Basically it is a logic circuit that will convert the separate turn signal and brake lights to a left side turn/brake combo and a right side turn/brake combo. I had to put one on my Toyota truck with separate turn signals and brakes. I found one at Pep Boys that lasted the life of the truck.

Thanks, it seems to be that’s what I need to do. I apreciate the help.