If your heat is not working, start by checking the thermostat. Is it turned on and set to heat? Try setting the temperature 2 to 4 degrees above room temp. (When troubleshooting heat pumps in cooling mode, follow this same process but set the temperature below room temp instead of above.) Switch the fan on.
If the fan doesn't start , check the fuses and breakers. Replace the fuse or flip the circuit breaker to the closed position and determine the cause of the overload. You may have a bad connection, a seized blower motor or a shorted controller board. If you didn't blow a fuse or trip the circuit breaker, old or worn-out wiring on your heat pump may be the cause . Wiring or loose terminals will need to repaired or tightened. It could also be defective thermostat or a stuck fan relay.
If your fan is running , but you still feel cold air at the normal setting, check to see if warm air is coming out of the vents when the thermostat is set to emergency heat. Make sure the thermostat is at least five degrees above room temp. If you feel warm air, then the problem is with the outdoor unit. If you don't feel warm air, you may have a defective thermostat or air handler to blame.
Once you've determined the problem is with the outdoor unit, return the thermostat to normal from the emergency heat setting. Wait a few minutes before investigating the outside unit. When you inspect your unit, do you notice ice or frost building up on the outdoor coil? This may indicate a defective defroster timer or control module, or the unit could be low on refrigerant. If there is no frost check to make sure the airflow isn't blocked by debris – grass clippings, sticks, leaves and weeds can all accumulate and prevent air from going in and out. Also check to see if the outdoor fan is running. If not, there may be a problem with wiring, the fan motor or compressor run capacitor.
If you are unable to diagnosis and fix the problem with your heat pump, or if you have additional questions, contact your local Trane Comfort Specialist. A certified technician will help you correct the problem and keep your home at a comfortable temperature.