My Outside Unit is Making a Loud Buzzing Noise. What’s Wrong?

In the winter we get customers calling in about their outside units making a loud noise quite often. We live in Florida and only a few weeks out of the year does it get below 38 degrees. When it does drop below this temperature, we start getting a lot more calls about outside units making noises, heating not working as well as it should, and thermostats not reaching set temperature. Most of the time customers have their thermostat set to regular heat and their system is going into defrost time and “short-cycling.”



What is defrost mode? Defrost mode only applies to Heat Pump systems. Defrost mode is the process your heat pump uses to remove built up ice from its coils. In wintry weather, the outdoor coil gets so cold that it starts to freeze. Ice builds up, and the coil becomes blocked, which forces the system to work harder for less output. Defrost mode periodically melts this frost by briefly reversing operation, sending heat back to the coil outside and melting off the ice. Defrost mode is a safety feature that keeps your system running properly in freezing conditions.

When the temperature is around freezing, your system will start “short-cycling.” This is the term that describes when your outside unit freezes, then defrost mode comes on to melt the ice, then your outdoor unit freezes again, and then defrost mode comes on again, and the process just keeps cycling repeatedly. This is not good for your system and we are about to tell you how to fix this.

When you know the temperature is going to drop below 38 degrees and get colder throughout the night, go ahead and switch your thermostat to the “emergency heat” or “auxiliary heat” setting. Both terms mean the same thing. They will both switch your system to operate solely on your electric heat strips which are located inside your indoor air handler or located inside your package unit if you have a heat pump package unit. Either way, this will prevent your outside unit from operating inefficiently and short-cycling when the temperatures start to dip.

If you hear a loud buzzing noise and it seems like your unit is not heating right in very cold temperatures, switch your thermostat to emergency heat and that might solve your problem. If not, give us a call and we will be there shortly to make sure you stay warm.