4-Pole to 7-Way Wiring Adapter 37185 Connection for 2007 Ford F-150 and 1978 Terry Travel Trailer

Question:

my trailer is a 1978 terry travel trailer. my kit has : white ,yellow,brown,black, green, blue, and purple. my trailer doesnt have purple. it has red. do I have the wrong kit. its a Hopkins 37185

asked by: Lonnie H

Expert Reply:

The Hopkins 4-Pole to 7-Pole adapter # 37185 you mentioned is not a vehicle-specific product; it can be used on any vehicle with 4-pole wiring to allow upgrading to the 7-way format that includes additional circuits for a trailer's brakes, 12V power and reverse lights. If your 2007 Ford F-150 has 4-pole wiring this item can be used to allow making those additional circuit connections. The linked image shows how the additional wires/circuits on this item are usually configured.

The wire colors on a trailer are not always a reliable way to know what each one does. There are certain common function/color assignments but there is not any guarantee that any given trailer's red wire will carry the same function as another trailer's red wire. Testing is the way to know for sure. This is easy to do.

Use your vehicle's battery or a well-charged 12V spare battery to test each circuit on the trailer. This will tell you what each one does. A set of jumper cables and two lengths of wire will make this easier. Connect the battery negative terminal to the trailer's ground wire (usually a white wire, but it will be the one that is attached to the trailer frame). Then, one by one, apply the battery positive wire to the pins or wires on the trailer to see what function is activated.

The usual trailer wiring configurations are detailed clearly with photos in the article that I linked for you. The article shows the usual wire colors, but again, it is likely that your 40-year-old Terry may have been re-wired at some point.

expert reply by: Adam R