I agree, if it didn't hum before but now is then it sounds like something is breaking down. To be on the safe side uncouple the MH from the EHU if you are leaving the vehicle unattended for any time. Just to be on the safe side.
Hi, Ken, wait till we get back on Saturday, how come you have hook up problems, when we left you were on battery/panel only, have you tried reversing your two pin plug into the hook up, might work, might not. Remember this number in case you have to call some of my work mates. 112.