Installing a 7-Way Connector on a 1999 GMC Yukon and Wire Functions on 1981 Coachmen Travel Trailer

Question:

I have a 99 Yukon and it is marked for colour line up but How do i find out the colour and what each wire does.from my truck. It does not have plug and play connectors. so I have my reg 4 pin which is simple and my blue and orange which are trailer brake and power. what if my trailer wires are for some odd reason different colours and gauge of wire...I have notices same colour match but different gauge on trailer. does this mean it could be for something different. ... my trailer has an odd greenish yellow neon wire. not sure what it is lol and a red one. my truck does not. Trailer is a 81 ...31 ft coachman travel trailer. I have had no success in finding the wiring diagram for it so i may match the wires up. very frustrated and was recommended to you all. oh it is Hopkins connectors and Tekonsha controller.

asked by: David S

Helpful Expert Reply:

The first thing you should know is there isn't exactly a standard for wire color/function. You pretty much have to ignore wire colors and instead wire by function in many cases. There are some constants though such as tow package wire bundles under the dash of certain Chevy and GMC vehicles, but not the 1999 Yukon.

On your 1999 GMC Yukon the other ends of those blue and orange/red wires are very difficult to access so it is recommended to hardwire in a 7-Way trailer connector and a brake controller rather than attempt to use those factory wires. To do this you would need plug your 4-Way into # ETBC7 and hardwire the remaining wires to the vehicle and brake controller. I have included some links that show and explain this installation for you.

For 1981 Coachmen travel trailers the factory wiring is as follows:

White is ground
Red is stop and left turn signal
Brown is stop and right turn signal
Green is tail/running lights
Blue is for electric brakes
Yellow is for reverse lights
Black is for 12 volt power

If you have any different wire colors then you will need to determine the functions another way. To determine the wire functions on the trailer you could either try to physically trace each of the wires to see where they go or you could use a 12 volt battery and apply power to each of the wires and see what lights up or turns on. This is probably the easiest method to find the functions of those wires.