Being warm weather people use Hydrohot heat in coach less than 85% of time Mostly AC to cool. But it never fails. Almost very year in Jan or Feb when we finally get freeze nights in North FL I go the plugged in MH at the house to turn on the Hydrohot for heat at night to keep a 40*-45* temp. inside to keep pipes from freezing and the find NO HEAT. Turned on electric, set thermostats thought all good. Next day found out no heat. At first thought maybe electric element bad so turned on diesel sw. It ran thru a cycle and shut off nothing but cold air at exhaust. Thought diesel controller bad again. Believe it only used to control burner? Then checked amps to coach electric and read 12 amps so element must be on. Opened access to Hydrohot felt outlet pipes to feel heat pipes to units inside coach and lines warm so electric is working fine but pumps will not run to put heated fluid into the units and coach will not warm up inside. No warning lights on Hydrohot panel, Green status light lite, Low temp green lite to show heat available. WHY DO CIRCULATING PUMPS NOT RUN? What do I look for to fix?