Your thermostat isn’t working properly — If you suspect an HVAC malfunction, the first thing you should check is your thermostat. In many cases, simply resetting the thermostat or replacing its batteries will solve the problem. However, if you’ve performed thermostat troubleshooting and the air handler doesn’t seem to be responding, then it may need to be looked at by your HVAC technician.

Poor air circulation — If the rooms in your home aren’t receiving warm or cool air, this could be due to a combination of one or more issues affecting your air handler, such as leaks in the ductwork or malfunctioning dampers. If the cause is a clogged air filter, you should be able to replace it without the aid of an HVAC technician. A typical whole-home air conditioning system requires a new air filter every three months — or once a month during seasons of heavy usage.

A noticeable decrease in indoor air quality — In addition to distributing conditioned air, the air handler also removes stale air from the room, along with indoor air pollutants like dust and other particles. Signs of decreased indoor air quality, such as when odors seem to persist within the room, indicate problems with the air handler.

The blower motor isn’t working — A blower malfunction can be caused by a bad relay, issues with the control board, or a capacitor that needs to be replaced. In any case, you lose airflow if the blower stops working. Air handlers rely on airflow to deliver conditioned air where it’s needed, so a malfunctioning blower will only increase the workload on the heating and air conditioning systems.