1. Do as the other poster stated. Wire the 120 element direct. Then use a simple plug in xmas type timer to turn the element on and off. probably run for 20 hours and then off for 4 hours until you get a handle on the time really needed to prevent freezing the lower section.
2. Yes, your refer is a Euro and Canadian refer. Not even available in the USA. So, Dometic does not have the parts readily available. We have been waiting on the control module since July on a 8555. Are you POSITIVE the refer has 12 volts supply to the back input connection? Doug
