Troubleshooting Electric Trailer Jack with 7-Way Plug That Does Not Function Consistently

Question:

Hooked up the trailer jack to 5 different vehicles with no luck. Jack is prewired with 7 pin connector. Then when I was about to return the unit, low and behold it worked on the 6th truck. Obviously this means a malfunction on the vehicle side but what are the odds that all 5 would not work? What should I do next? I checked with an ohmmeter on one of the trucks and Im getting 11+ volts but still the jack doesnt work.

asked by: Robert B

Expert Reply:

An electric A-frame tongue jack like # EJ-3527-BBX or # 3370093500 that has a pre-wired 7-way plug will rely on the ground and +12V contacts within that plug to deliver operating power. Jacks may not function with less than 12 volts. Those contacts are located, respectively, at the 5:00 and 11:00 positions on the plug as you look at it. Please refer to the linked photo. You might try an aerosol electrical contact cleaner like Caig De-Oxit to see if that restores reliable operation.

I agree that it seems unlikely that all 5 vehicles you used to test the jack would all have the same issue. I think what is more likely is that either or both the ground and +12V contacts on the jack plug have corrosion or are bent. Either of these conditions could prevent the motor from getting the current it needs to function.

You can best test the jack by completely bypassing the vehicle wiring; use a well-charged vehicle battery and lengths of wire. This direct battery power should operate the jack without issue so long as the battery is well charged. If it works this way but not when connected to a vehicle 7-way then you will want to inspect/clean the contacts on the vehicle socket too.

If you have a multimeter like # PT89ZR you can test the actual voltage available at the vehicle 7-way.

expert reply by: Adam R