Thanks JimboFunFinder, I guess what I meant by heat pump is our other trailer (a Chalet pop-up) you can use the A/C to heat as well as cool. It does not get hot, just warmer air by reversing the flow - just like any A/C if you feel the air being pumped out the back is warmer (see models linked below for similar feature). I cannot turn on the heat via the thermostat without the A/C turning on as well, that is why I wondered. The thermostat has just fan, heat and cool option along with temperature. Maybe it has failed then?
I did find a thread on the stabilizer jacks. Sound like mine might need a good clean and possibly some silicone near the wires to protect them from corrosion. I can see it starting in. I guess the rear particularly is prone to water getting in the unit.
I will investigate the converter closer and get that sorted with the battery when it is not so freezing cold outside. It had been kept in a garage till now, but it is in my driveway for a week or so until I can get it into storage (temporarily until our new home is finished).