By pass the thermostat, heater valve comes on and stays on, attach it to the thermostat , it quits working, works sometimes though, like it should, but then after a while, it stops working, attached the wires direct again and the heater works, try to put the wire back on the thermostat to see if it will work again and it doesnt,. take the wire off and hold both wires together and the heater works fine,,.. need to replace the thermostat, where can one be find for the small voltage thermocouple?

Heating & Cooling - Cozy - (W352E) Heater