Arrived at home and theist was blank. Checked high voltage into the unit and low voltage out of the unit. All were good. Took thermostat off of all and there was 27 volts. Put thermostat back in the wall and the throat came on. Informed customer that I could replace the thermostat if he wanted, or that he could but his own and we could install it should the thermostat goes bad. Unit is heating fine.