Test a High-Limit Switch(Propane Heater)

Test a thermal switch (aka high limit switch) on a DESA brand propane construction heater.

The thermal switch is a safety device that will shut the heater down once the ambient temperature reaches approximately 85℉

According to the manufacturer, DESA International:

To check the switch, set the ohmmeter on the “RX1” scale. With the heater cool,

check for continuity across the thermal switch by attaching the ohmmeter to the

blue wires on the switch. The ohmmeter should read “hot” until the ambient temperature reaches 85F, at which time the meter will read “dead”.

If the switch shows “dead” at any other temperature range, then the part is defective and should be replaced.

(Note: this test must be performed in an area that is cooler than 85℉ )