Troubleshooting Electric Jack Whose Light Works But Motor Does Not

Updated 03/28/2019 | Published 03/26/2019

Products Featured in This Question

Lippert Electric Trailer Jack with Footplate - A-Frame - 18" Lift - 3,500 lbs - Black

(436)

$259.95

7-Way Round RV Style Trailer Connector - Trailer Side

(415)

$14.47

Question:

I recently pulled a trailer for a friend that has an electric jack wired directly to its own 7 pin plug that you connect to the tow vehicle. My truck would run the light that is on the jack, but not the jack. His truck would not run either. The jack works, as we found multiple other trucks that would run the jack. This jack is wired to the auxiliary 1 o clock of the plug so it would get power from the aux on the truck. My truck runs the light, so it is getting power. I checked the aux on my truck with a test light and it is getting power. I can run the interior lights on the trailer, which should be wired to the same circuit... So why can we not run the jack with our trucks? Any suggestions?

asked by: Tim

Expert Reply:

Thank you for detailing the issue and the testing you've done for the electric jack.

My suspicion is that the jack's plug has a weak ground connection. A weak ground will pass enough power for the jack's light to function but may not pass enough current for the jack motor to operate. This is not uncommon on trailers that are a few years old and which may have developed some corrosion on the plug contacts.

Check the ground and +12V contacts on the jack's male 7-way plug. Please refer to the photo. You can try an aerosol spray electrical contact cleaner like Caig De-Oxit to see if that helps. But if corrosion has migrated through the inside of the 7-way plug then you'll need to replace it with a plug # A7WCB.

expert reply by: Adam R