Troubleshooting Operation of Electric Trailer Jack That Only Works with RV Shore Power Connection

Question:

Power jack on my 32 foot RV trailer works when its plugged to 110, but doesnt work when hooked to the 12V on the truck? What could be the problem?

asked by: Bo P

Expert Reply:

If your RV electric tongue jack functions properly when your trailer electrical system is connected to shore power (an AC outlet) but not when it is powered by the truck's 12V auxiliary power circuit then either the 7-way connectors on the truck and/or trailer could have corrosion on their contacts or the jack's motor may simply require more power than the truck's 7-way circuit can deliver.

Electric tongue jacks can draw a lot of current when working near their maximum capacity. For example, the Stromberg Carlson electric jack # JET-5000 needs a full 30-amps to lift its 5000-lb rated maximum load.

You can check your jack to see if it has a rated maximum current draw and also check the truck's power box or owner's manual to see what fuse rating protects the 12V circuit. If you jack needs 30-amps and the 12V circuit on the 7-way is rated for only 25-amps then that tells you it is a matter of insufficient power delivery.

If this is a new issue then try cleaning the contacts on the truck socket and the trailer plug with an electrical contact cleaner like Caig De-Oxit. On the truck side clean the contact at 1:00; on the trailer plug clean the mating contact at 11:00.

expert reply by: Adam R