Why Do 4 to 7-Way Trailer Connector Adapters Have Missing Pins Inside the 7-Way Plug

Updated 04/30/2020 | Published 04/29/2020

Question:

I previously purchased the adapter from elsewhere in the attached picture. I have a 1995 F-150. This adapter does not work and I’m looking for the proper adapter. The adapter fits, but the issue is this adapter and the adapters you sell seem to be “missing” wiring. My trailer wiring takes all 7 pins, the pin that would connect in the 11 o’clock position is + power, but as you can see from the picture, there is no plug there to receive that power, in fact it’s missing 3 plugs total that power different aspects of the trailer. Why is this? When I tested my harness for power I was getting the voltage needed from + power. When I plugged in my adapter and tested I got nothing. When I looked closely at it I realized why there’s no plug in the adapter that actually connects to power. I don’t understand why this is and am looking for advice. Thanks!

asked by: Joshoua R

Expert Reply:

In order to convert a trailer from a 4 or 5-way flat to a 7-way round you will need to use the Trailer Wiring 7-Way Upgrade Kit w/ Junction Box part # HS381-9000. The reason for this is because 4-way or 5-way flat trailer connector only carry circuits for stop/turn, running, and sometimes reverse lights. The 7-way has all of these circuits as well a brake output and a battery charge line.

expert reply by: Conner L