There are many types, brands and models of heat pumps, and a wide range of problems that can happen. There are, however, some common problems that are seen.

Before going further, check a few basics. Check the main power switch on the heat pump, just in case. Turn both switches on if it is a remote system.

For heating, make sure that the thermostat is set higher than the ambient temperature in the room, and that the selector is set to “heat”.

Likewise, for cooling, ensure that the thermostat is set lower than the room temperature and the selector switch is set to “cool”. For programmable thermostats and digital controls, check to make sure the batteries are fresh and hold a charge.

Next, check if the air handler is functional by moving the fan switch from auto to on. If the blower runs, it is okay, but if nothing happens, then have a technicain check any circuit breakers on the air handler cabinet as well as breakers or fuses in the main panel. He/she will reset or replace tripped fuses/breakers and proceed with the troubleshooting if needed.

Note: The following troubleshooting points are meant as a guide for consumers. Only qualified and experienced HVAC technicians should do repairs involving the internal components of heat pumps. The high voltages used in internal controls and wiring can result in serious injury and even death. Do not attempt to open any of the panels on the heat pump.

Also, the sale of refrigerant is strictly regulated by the E.P.A. in the U.S., and you must be a certified HVAC technician to perform maintainance involving refrigerant containing appliances. Call the HVAC guy and let him do his job.

Noisy or Inefficient

If the pump operates, but is noisy, the problem is either loose parts or loose drive belts. Check all the setscrews on the blower and fan blades, adjusting and tightening thrust collars. Also, adjust all belts or replace if necessary.

If the problem is not enough heating or cooling, the outdoor coil could be obstructed; stray objects like insects, vegetable matter, bird feathers etc. may need to be cleaned out. The air filter may also be dirty or clogged, so clean or change it if necessary. Also check supply or return grilles and screens, as these may become blocked by debris, and clean as required.

Reversing Valve Problems

Sometimes the reversing valve fails to shift from heating to cooling. The problem may be in the coil. A coil may be defective and need to be replaced, or it may not be receiving any voltage, in which case the electrical system will need repair.

The lack of reversing can also be due to low refrigerant level, or “charge”, possibly because of a leak. The system will need to be recharged with refrigerant by a licensed technician (this is never a DIY project).

There may be a leak in the piston cup, clogged pilot tubes, clogged pilot valve bleeder hole. With these causes, it may be necessary to replace the reversing valve, although certain operational sequences can be attempted by the technician to free clogs or reset the system

At other times, the reversing valve may begin to shift without completing the reversal process. There are several possibilities here. The valve itself may be damaged and require replacement. The compressor may not be supplying sufficient pumping volume to maintain the reversal, causing the valve to hang in mid-stroke.

Alternately, it could be there is not enough of a pressure differential. These can be cured by adjusting the head pressure, but the reversing valve may have ports that are too large for the system and may need to be replaced with one having smaller ports.

Compressor Problems

Heat pumps used in residential applications have compressors that are hermetically sealed with the motor and pump in a welded housing unit. These cannot be repaired if they are at fault and must be replaced. Failed units are sent to a service center to be overhauled and reconditioned.

Compressor motors can burn out if the heat pump is operated with a low refrigerant charge, a fan motor not working or excessive buildup of ice or frost.

If the compressor will not start, it may be due to a blown fuse or tripped circuit breaker. If the problem persists after fuse replacement or resetting the breaker, the compressor is probably grounded out and must be replaced. It also may be caused by loose wiring that can be replaced/repaired or defective run or dual capacitors that can be replaced.

If you hear a sharp pitched noise after the compressor shuts down, this is normal; it is the sound of pressure being equalized across valves in a piston type compressor. However, if you are hearing a constant hissing sound in the compressor, then you probably have a reciprocating piston compressor with defective valves, and the compressor needs to be replaced.