How to Replace a 7-Way Flat Pin Socket Connector on Your Tow Vehicle

How to Replace a 7-Way Flat Pin Socket Connector on Your Tow Vehicle

On our last trip, the plastic flap covering our tow vehicle’s 7-way hitch socket connector broke.  This doesn’t seem like a big deal, but without the flap, the trailer cable won’t stay in the socket since it relies on the flap’s flange to keep it in place while driving.  While we were descending a steep hill on our final leg home, our 2020 Volvo XC40’s brakes began to pump.  We had never heard this noise before, and then at about the same time an orange warning light lit up indicating a failure with the trailer cable connection.  We pulled over and found that our Scamp 13’s cable had pulled out.  This would explain the noise of the Volvo’s brakes working hard, since our Scamp’s brakes were disconnected.  The trailer cable is essential for the operation of the trailer’s brake and safety light system,  powering the trailer’s turn signal lights, brake lights, hazard lights, running lights, and also activating the trailer’s brakes. When the connector broke, all of these critical features no longer worked.  Fortunately, we had some zip ties which we used for a temporary fix to get us home.

I called Volvo when we returned home and was told that the connector is molded into the entire Volvo wiring harness and they don’t sell just a replacement flap.  They said the only way to fix it with Volvo parts is to replace the entire wiring harness, and the harness cost would be $167 plus labor!  This seemed to be a very high cost for just a broken plastic flap replacement.  Our 2020 Volvo XC40 has been a reliable workhorse for us, and I wanted to find a simple inexpensive solution to fix the broken flap.  Since we sometimes do off road boondocking, we wouldn’t want to have to replace the entire wiring harness any time the little plastic flap breaks.  Fortunately, I was able to find another solution at a fraction of the cost.  This inexpensive 7-way socket and mini harness currently sells for around $17 on Amazon.  I was easily able to replace the broken Volvo 7-way socket connector with this new connector by joining this new mini harness to the existing Volvo wiring harness.

This new 7-way flat pin socket connector should work with most tow vehicles as long as the wiring colors/pin locations are the same as the existing vehicle’s wiring harness colors/pin locations.  To make sure everything works well, the first thing to do is test the continuity of each of the new connector’s 7 wires (with a continuity tester) to verify that the wiring and pin locations are identical by color to the tow vehicle wiring.  If each of the wire colors is continuous with the same pin locations on the new connectors as the tow vehicle’s 7-way socket connector, everything should work great.   I noticed on our Volvo, the center pin wire on the Volvo wiring harness is purple, but the center pin wire on the new connector harness is red.  So, I just had to connect the purple wire to the red wire so the Volvo continues to send the correct signal to the center pin of the new 7-way socket connector.  All the other wire colors/pin locations on our Volvo’s old connector did correspond to the new connectors’ wire colors/pin locations.

Once confirming wire colors and pin locations are matched, I verified that our Scamp cable plugs securely into the new 7-way socket connector.  I then clipped the wires from the existing Volvo 7-way socket connector, unbolted it and removed it from its mount.   Once removed, I also verified its wire colors and pin locations with a continuity tester.  I then attached the new 7-way socket and mini harness to the Volvo’s existing wiring harness, making sure to pull the new mini harness through the mounting hole before making the connections.  I stripped each wire and then used the provided preinstalled butt connectors to join each of the wires (by color, except for the purple/red combination).  For the white wire, I used a WAGO connector to connect the two white wires since the white wire on the original harness is already grounded (I just clipped the circular grounding connector from the white wire on the new mini harness and joined it to the white wire on the Volvo wiring harness).  After the wires were all connected, I mounted the new connector with the existing bolts and tucked the wiring harness up behind the bumper (and used Gorilla tape to help keep it in place).

To test the system, I connected the Scamp’s trailer cable to the tow vehicle and ran the Volvo’s automated trailer lights check.  I observed all lights working properly.  The key to doing this installation successfully is to make sure to correctly match each of the wires to the proper flat pin locations.

Project Supplies and Tools:

1. Anto 7 Way Trailer Plug: https://amzn.to/3xXw11z
2. WAGO 221 Connectors: https://amzn.to/3Nn2Hr8
3. Wire stripper:   https://amzn.to/3M6CyME
4. Continuity Test: https://amzn.to/39T82J7
5. Gorilla Tape:  https://amzn.to/3Nh6y9a

Disclaimer:  You will get the same great Amazon price by clicking on the links here compared to buying directly on Amazon, but by buying here you will also be supporting the continuation of this website as we get a small commission from each sale.  These are products and procedures we use for our own Scamp that we selected and developed from our own research and experiences.  However, we do not endorse any specific product and cannot guarantee that the products we use are exemplary and the procedures we use are complete, accurate, detail the correct recommended procedures, or apply to your model small travel trailer.  It’s always best to double check with your manufacturer or operation manuals to ensure you are doing everything correctly.