Reasons Your Heater Kicks On When Your Thermostat is Set to Cool

Reasons Your Heater Kicks On When Your Thermostat is Set to Cool

Reasons Your Heater Kicks On When Your Thermostat is Set to CoolIt’s unnerving when your HVAC system is in cooling mode and you feel warm air coming from your registers. This can occur for various reasons like a mix-up in basic HVAC settings, neglected routine maintenance, or at worst, a newly-developed problem with the cooling components. Here’s how to identify and solve the most common issues, and know when to call for professional help:

Recheck Your Thermostat Settings

Mix-ups with your thermostat settings can produce warm air output instead of cool, and they’re easily fixed:

  • The thermostat was accidentally switched over to “heating ” mode and just needs to be reset for “cooling.”
  • The fan setting is in the “on” position, which keeps it running non-stop and sends warm air out in between cooling cycles. Put the fan on “auto” instead, and it will operate in tandem with the A/C and only push cool air through the ductwork.

Check Whether the Outdoor Unit is Operational

If airflow from the registers suddenly goes from cool to warm, there may be a loss of power at the outdoor unit. If it’s non-responsive, check both the outdoor emergency shutoff switch and the unit’s breaker in your home’s main electrical panel. If either has tripped, resetting it may be all that’s necessary. If a reset safety device quickly trips again, leave it alone and call your HVAC pro to determine why.

Look for Airflow Restrictions

A drop in airflow through your HVAC system can lead to coil icing and/or a compressor shutdown that leaves you with warm air output when it should be cool. Sometimes, putting in a clean air filter, making sure all the supply and return vents are fully open and unobstructed, and clearing away debris/vegetation that’s blocking airflow at the outdoor unit can help. If there’s no improvement, call your HVAC technician to check for more serious issues, like a low refrigerant charge, a malfunctioning fan, or a dirty evaporator or condenser coil.


If the cooling system in your Peachtree City home is producing warm air, and adjusting your HVAC settings hasn’t helped, contact us at Powers Heating & Air for expert assistance.


Our goal is to help educate our customers in Peachtree City, Georgia and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about other HVAC topics, download our free Home Comfort Guide or call us at 770-487-2040.


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