The condensing coils in the outdoor condensing unit of a central air conditioner are responsible for performing an important phase change on the refrigerant. The refrigerant moves from the compressor through the condensing coils and then into the house to cool the evaporator coils and your home. Problems in and around the condensing coils can create a hiccup in the initial phase change and create problems with the entire cooling process.

The various parts in the condensing unit are fairly correlated, and a problem in one can easily lead to a malfunction in the condenser coils. Here are two other parts of the condensing unit that can cause problems in the condenser coils.

Compressor Doesn't Stay Running or Won't Pump Out Gas

The thermostat in your house sends an electrical signal to the condensing unit to start up the compressor, which compresses the gas refrigerant to pump it into the coils. The compressor requires a sturdy, steady electrical current to stay running. One or two different types of capacitors or energy boosters are in the condensing unit to help ensure the compressor doesn't shut down if the electricity has an interruption.

If your compressor does suddenly stop working, the problem might lie in those capacitors. And the non-working compressor can't pump out the gas refrigerant the condensing coils need to perform the proper phase change.

Most central air conditioners have at least a run capacitor, which ensures the current stays steady during the compressor's normal operation. But some units also have a start capacitor, which offers a boost at the compressor's startup. You can usually tell what capacitor is the problem by whether the compressor can start up at all or if it stops running abruptly after some time.

You can test the capacitors using your owner's manual and a multi-meter. Make sure you turn off the power to the unit before you try to test and drain the charge out of the capacitors before testing. The start capacitor drains with the AC setting on the multi-meter and the probes hooked to its terminals. The run capacitor drains with the end of an insulated screwdriver across its probes. Then simply test each capacitor for Ohms of resistance and make sure each reading matches the label on the capacitor.

If the readings don't match, call an air-conditioning services company for new capacitors.

Blower Fan Doesn't Spin Fast Enough or Has Stopped Working

Condenser coils naturally become warm due to the phase-change process, which reverses in the evaporator coils and turns those coils cold. The warmth of the coils doesn't reach a dangerous level in part due to a motorized blower fan that points at the coils and circulates ambient air to maintain a healthy temperature.

If the blower fan slows down or stops working, the coils can become too hot and can trigger a safety shutdown that turns off the entire system unexpectedly. You should see a warning on your system's readout that the safety shutdown occurred.

You can check the fan by first listening to the unit while it does run to hear whether the fan is running at all. If the fan isn't running, call in an air-conditioning services tech to replace the fan motor. If the fan sounds slower and like it is clanking, your fan blades might have come a bit loose from the motor shaft, and that is a problem you can fix.

Turn off the power to the system, open up the unit, and gain access to the motor assembly by following the instructions in your owner's manual. Spin the blades gently around the motor shaft with your hand and check for wobbling. If there are wobbles, tighten the set screw at the connection point using a wrench. Put the unit back together and test the fan again. Problems still occurring? Call an HVAC technician.

Visit sites such as http://www.smedleyservice.com to find an HVAC contractor near you.