■ Check the settings on the thermostat. Is unit turned on and is the temperature high enough to be calling for the unit to operate.
■ If unit fails to come on, turn fan control switch of the sub-base to the constant run position. If the fan comes on, low voltage is present in the system. If it doesn’t come on, there is no low voltage in the system. Check at the transformer for secondary voltage. If not present, check the primary.
No primary voltage — Check fuse that supplies the unit.
No secondary voltage — Bad transformer.
Both primary and secondary voltage present – Check at sub-base of thermostat for 24 volts.
Voltage present at sub-base — Replace sub-base and thermostat.
Voltage not present at sub-base — Control wiring from transformer to thermostat defective.