I have this unit installed in a 09 montana rv. I push power 1x and then push time 1 min. heats water beeps END and all sounds stop. Then if i place something else in to heat, using same procedure as above. this time at END it beeps and "something" keep running, even though it shows END. this noise (fan)??? will run for about 2mins. If i open the door nothing happen or if i push stop nothing happens just keeps running. thanks you for your time