HappiJac 4150 Problem

A ball screw is a shaft with a thread profile that looks semi-circular, and the nut that runs on it has recirculating balls that fit in the groove on the shaft and mating groove in the nut. They are much lower friction than a standard threaded nut, and are used for high loads. An ACME is simply a threaded nut, though the ACME load bearing thread profile is used rather than UN or some other bolt or screw profile. ACME should be pretty much failure proof. It could be a stripped nut or shaft, that seems unlikely. If it held the load, but wouldn't turn, then you would suspect the drive with does have a pin through the gear and shaft. The ACME screw anchorage at the top of the jack could not have failed or you would see the screw itself poking out of the top of the jack. However the nut is fastened up inside the top of the lower tube, that could have come adrift and is simply walking down the inside without pushing the tube down (and the camper up). The nut is on a plate that is just crimped in place (or it was on mine of 16 years ago).

Happijak used to offer a repair service that was a pretty reasonably flat rate, don't know if that is still on - you would have to phone them and ask.