etrailer Electric Trailer Jack Not Running With Vehicle 7-Way
Updated 06/19/2026 | Published 06/15/2026
Question:
I just installed a new e55zv jack onto my travel trailer. This replaced an original lippert jack. I connected the red wire to the same red wire that provided power before to the original jack, and I also ground the black wire to the frame. The lippert jack only had one red wire. My question is, the jack works with the auxiliary battery but doesnt work when I hook it to my 7pin plug on my vehicle. The lippert jack did.
asked by: Tim
Expert Reply:
Hi Tim; since the # e55ZV works with the battery we can rule out the wiring as the issue. I'm not sure how you have it connected to the 7-way, but it isn't getting enough power off of your 7-way to run the jack. Most electric trailer jacks are intended to operate with the trailer battery connected, with the 7-way charge line helping maintain the battery rather than powering the jack directly.
What kind of vehicle do you have? Some vehicles won't activate the 12V circuit if the computer doesn't think it is hooked up to a trailer so that is another possibility here.
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Product Page this Question was Asked From
etrailer Electric Trailer Jack - Drop Leg - A-Frame - 18" Lift - 5,000 lbs
- Trailer Jack
- Car Hauler
- Enclosed Trailer
- Utility Trailer
- A-Frame Jacks
- 4001 - 5000 lbs
- Electric Jack
- 18 Inch Lift
- Bolt-On
- With Round Foot
- etrailer
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Dan A.
6/19/2026
I agree with Robin make sure your Trailer battery has clean connections and fully charged, I don't think the wiring on your truck is heavy enough to run a jack of this size, Your truck will help keep your trailer battery charged.