Abstract: A portable thermostat testing device for testing the trip temperature of a thermostat includes a testing block having a smooth, flat top surface, heat dissipating legs, a bore and a pair of grooves. A heater is positioned between the pair of grooves and a temperature probe is inserted in the bore. A fan is used to transfer heat to the testing block through convection. A thermostat to be tested is mounted on the top surface and the continuity of the thermostat's switch is monitored by a continuity checker. The testing block is heated by the heater and the temperature across the top surface is kept substantially uniform. The trip temperature is sensed by the temperature probe when the thermostat's switch opens. The testing device is mounted in a sturdy carrying case.