What do AUX, EMER, and MALF indicators mean on my HEAT PUMP THERMOSTAT?
AUX – Auxiliary Heat or the second stage of heat in the Heat mode. This is energized when the Heat Pump is not keeping up with the thermostat setting. It is normal operation with most pumps for the thermostat to call for auxiliary heat. If the auxiliary heat and emergency heat are using the same back-up heat source the thermostat may also show the Emergency Heat light whenever the Auxiliary heat is on. EMER – Emergency Heat. When switched to Emergency the thermostat bypasses the pump and uses the back-up heat. This is useful if the pump is not operating correctly or if the temperature outside is so cold that the pump is not economical to run. If the Auxiliary Heat and Emergency Heat are using the same back-up heat source the thermostat may show the Auxiliary and Emergency Heat light on at the same time. MALF – Malfunction. Malfunction indicates the heat pump system is sending a signal to the Malfunction Indicator on the thermostat terminal marked L. It does not indicate a malfunction i