How to Change Wiring of 1977 Amerigo Camper Trailer to Match 7-Way Format on Tow Vehicle

Question:

So confused about this wiring, the camper is totally gutted but I have only 4 wires running all exterior lighting red yellow going to all amber and red marker lights and I have a green and blue wire I’m assuming are running the tail lights... I have a 7 prong plug on my vehicle. I would scrap all the wiring but all the marker light are behind the overhead cabinets. Help...

asked by: Jacque

Expert Reply:

No worries. If your trailer does not have brakes its wiring may well be the simple 4-pole format using connectors like the one in the linked photo. The photo shows the usual wire colors and functions associated with each pin BUT wire colors alone are not a reliable way to know how to wire up the trailer, especially an older one. Testing is the way to go and it is easy enough to do.

You can confirm what wire does what on your trailer by using a charged 12V battery (like the one in your tow vehicle) to directly apply power to each wire to see what that circuit does. First connect the battery NEG to the ground pin/wire which will usually be white. You can confirm which wire is ground if you can find the one that connects to the trailer frame. Then one by one apply the 12V+ battery power to each of the other wires to see which function activates.

Since your vehicle has a 7-way wiring setup I suggest using junction box # HS381-9000 on the trailer. This item allows the trailer wiring to match the vehicle (without adapters that can be a pain)
and it enables you to make the wiring connections inside the box using ring terminals such as # 44-5310A.

I included a helpful article on trailer wiring that illustrates all popular wiring formats and connectors and how each should be configured.

expert reply by: Adam R