Understanding HVAC Issues

Investigating AC Fan Electrical Issues

The air conditioning unit that sits outside your home produces a great deal of heat. Heat must be expelled from the device, or the motors, pumps, seals, and other parts may overheat. Also, if heat is not removed, then the coolant may remain warm and will not cool air effectively. Heat is moved out of the unit with the help of an exhaust fan. This is the large fan that you see on top of the air conditioner. If you do not see this fan moving, then overheating is a serious concern. Turn off the air conditioner immediately and troubleshoot the fan. In some cases, electrical components may not be functioning the way they should. Find out how to test for electrical issues.

Test The Capacitor

If you hear the motor running inside your AC condenser, but do not see the fan moving, then there is a chance the fan is bent or stuck in place due to debris. You should check to see if this is the problem first. Turn off the AC unit, and use a screwdriver to remove the cover from the fan. Clean the blades with soapy water and a rag, and gently bend the blades straight if they appear bent. Turn the unit back on to see if the blades move. If they do not, then there may be a problem with the fan capacitor.

You can complete a simple test to see if the capacitor is working or not. Find a long stick and gently spin the fan blades clockwise. If the fan blades move, gain speed, and continue to spin, then the motor is working correctly, but the capacitor likely is not. 

The fan or run capacitor is a device that provides the fan motor with a boost of electricity to start it. The capacitor is much like a battery that holds energy, and it can fail and prevent the fan motor from starting. Capacitors will bulge, appear discolored, or form a layer of rust when they break, so you can look for these telltale signs when trying to figure out whether the part is working or not. Turn off the air conditioner and remove the fan cover. Release screws or clamps that keep the fan in place. The fan motor will sit just underneath the fan and will be wired directly to a small control panel. In between the fan and control panel wiring will be a small round device. This is the run capacitor. 

Inspect the capacitor for signs of wear and look for a sticker on the part that identifies the part number. Speak with your AC professional about ordering a new capacitor that matches the old one. The part can be wired into the same spot where the broken capacitor was installed. 

Investigate Motor Voltage

If the fan motor does not make a humming sound, if the capacitor does not look damaged, or if the motor does not work after a capacitor replacement, then the wires leading to the motor or the motor itself needs to be replaced. Locate all of the wires that connect to the fan motor. You may see a variety of different colored wires that run to and from the motor. The wire supply line that feeds the motor will typically be black. Follow this wire to the connection on the motor. Use a multimeter on this line to test for incoming voltage.

If the motor is not receiving any power, then try removing the end of the wire from the control panel and cutting about one-eight of an inch from the wire. Strip the cut end and feed it into the panel connector. Test for voltage again and turn on the AC system to see if the fan works.

If the fan still does not work or if the multimeter indicated that the motor was receiving power, then replace the motor. You can replace the motor by itself, or you can purchase a kit that includes the fan, motor, capacitor, and the wiring assembly. Kits are typically easier to install. Simply remove the old wiring from the control panel and replace it with the new wires from the fan kit. 

For more information and advice, contact a company like Allied Mechanical & Electrical, Inc.