Use these tips to diagnose and remedy problems with heat pumps.

Causes: No power to the unit or the thermostat not calling for heat.

Solutions: Check thermostat setting, electrical disconnect switch, and fuses or breakers. Most pumps have a "reset" switch in the outdoor cabinet.

IMPORTANT NOTE: If all electrical power has been off for more than an hour at temperatures lower than 50 degrees F, because of either a power outage or a tripped circuit breaker, you should not attempt to restart a heat pump for at least six hours after the power has been restored. Instead, turn the system selector to "emergency heat," wait six hours, then return to the normal heat setting; turning the system switch to "off" doesn't shut off the heater. This time delay gives a heating element in the compressor's oil crankcase time to warm up the system's lubricant and prevent valve damage.

Causes: An obstruction blocking the outdoor coil; malfunctioning blower unit; clogged filter.

Solutions: Clear the outdoor coil. Check the filter and blower unit.

Causes: Blocked outdoor coil could cause defrosting that lasts longer than 15 minutes or that occurs more than twice an hour.

Solutions: Check the outdoor coil. Leaves, snow, or other matter may be cutting off airflow through the coil. Clear the obstruction and the system should return to normal operation.

If it doesn't and the coil remains coated with ice, the reversing switch may be stuck. Try freeing it by switching your house thermostat to the cooling mode. If the ice remains on the coil after an hour, flip the system selector switch to the "emergency heat" setting and call a heating contractor for service.

See IMPORTANT NOTE above for information on restarting a heat pump.

Causes: Heat pump delivers a cooler flow of air than you may be used to. Also, indoor temperatures normally will drop 2 to 3 degrees when the outside temperature reaches the system's balance point differential, which is the point at which the backup heating kicks in.

Solutions: Minimize airflow discomfort by carefully balancing the duct system. To offset the balance point differential, you may have to raise the thermostat setting in colder weather.