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Troubleshooting Trailer Wiring After Using Adapter to Attach Vehicle 4-Way Flat to Trailer 7-Way


I just bought a 2015 flagstaff 627D pop up. It has a 7 pin wire and my car has a 4 way flat. I bought an adapter for it and when i plugged it all in my break lights and turn signals dont work? What would be the problem? Please help me out. Thanks for your time


Expert Reply:

I was unable to find your order number to determine the adapter you purchased from us so let's start with the correct one that you need, which is the Hopkins Endurance Quick-Install Trailer Connector Adapter - 4-Way Flat to 7-Blade # HM47200.

All you need to do with this is plug this into your vehicle's 4-way and connect your trailer's 7-way to it. The added wires of this adapter are not needed so you can simply tie them off.

If you do have an adapter like this already and you are still having problems you will need to do some standard troubleshooting. The first thing to do is take a look at your owner's manual to locate any trailer fuses or relays and ensure they are all there and in working order. If they are, in order to determine the specific problem you will need to purchase a circuit tester if you do not have one - the very handy Cordless Circuit Tester # PTW2979 would be my strong recommendation due to how easy it is to use - and test the connector on your vehicle after disconnecting it from your trailer. Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring.

If the signals going to your harness are okay, you'll need to test the signals coming out of the harness, and if they are correct then your issue is likely going to be with the trailer side wiring. You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you are going to need to either replace the plug or clean the corrosion. You'll also need to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion.

I have added links to a pair of help articles on trailer wiring, including a troubleshooting guide which I highly recommend taking a look at.

expert reply by:
Kyle S

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