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Troubleshooting and Repairing your Heat Pump

Published Sep. 23, 2016
By Gary Sprague

What do you do if your heat pump is not working properly? Some problems you can troubleshoot yourself, while others will require the attention of a heating and cooling contractor.

First Steps

If your heat pump will not run at all, here are three troubleshooting steps you should take before doing anything else:

  • Check that the electrical disconnect switch, which is usually located in a metal box mounted to the outside of the house near the outside unit, is not off. If it is, turn it on.
  • Check for a tripped fuse or tripped breaker in your main electrical panel.
  • Make sure the thermostat is on and set to either "Heat" or "Cool". Check that the temperature setting is not too high or low. Also check the thermostat batteries and change them if needed.

These are simple steps, but they can save you an embarrassing and potentially expensive service call. Here are a few other common heat pump problems:

Compressor Issues

A heat pump’s compressor circulates refrigerant and is considered the central component of the system. Problems with the compressor, including a seized or burned out compressor, often require replacing the compressor or, on an older heat pump, replacing the entire unit. Worn compressor bearings will also require replacing the compressor, unless the bearings can be replaced. A unit that makes a humming noise but will not start may just have an electrical problem, or a problem with the compressor overload relay.

Coil and Freon Leaks

A common heat pump issue is a coil that ices up. Among the possible causes is a unit that is low on refrigerant. This will prevent the unit from producing enough heat to melt the frost. Over time a heat pump may become low on refrigerant, but more often it is caused by a slow leak in the coil. The coil will need to be repaired or replaced, along with refilling the system with Freon. For safety reasons this should always be done by a professional, but adding Freon can be very expensive, often costing several hundred dollars.

Frost or Ice Build-up

Frost buildup can have other causes, too. It is often caused by improper airflow or heat transfer. One common problem is dirty filters which can cause a variety of problems to your system. For this reason it is important to clean or replace them regularly. A damaged blower fan can also cause the coils to frost up, as can a faulty control relay, broken defroster timer, dirty coils and, as mentioned above, a refrigerant leak.

Blowing Cold Air in Heat Mode

First make sure that the thermostat is on the "Heat" setting and not the "AC" setting. Check for frosting or icing over, as the unit can blow cold air if it is iced over. Check the filter and clean or change it, if needed. Other possibilities may require a call to an HVAC contractor and include dirty coils, valve problems, low refrigerant, or a problem with the fan motor.

A Noisy Heat Pump

Heat pumps can develop noises, some more serious than others. For instance, a grinding noise can be a sign of a problem with a fan motor – possibly worn bearings – which is a serious problem. A less serious problem is a rattling noise that could be caused by something minor like loose cabinet screws or loose ductwork, and which can usually be solved by tightening with a screwdriver.

Usually, keeping the heat pump components clean can help to prevent many problems. Dirt may make the compressor or fans fail before they should. Regularly clean or replace dirty filters to keep your unit functioning properly. Always keep the manufacturer's manual handy and if you don't have one, request one from the manufacturer.

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