Thermostat Set to Cool but Heater Blowing? Here’s Why

Thermostat Set to Cool but Heater Blowing? Here's WhyWhat’s up when HVAC settings don’t deliver the comfortable temperatures you’re expecting? Let’s assume the system is on and the thermostat mode is set to “Cool. ” When you feel airflow from the vents, however, it’s something closer to warm—almost like the heater’s on. If there’s an apparent disparity between your HVAC settings and what’s actually coming out of the vents, here are a few possible reasons why:

Is the temperature setting correct?

It’s an obvious thing—but we have to ask. If the system’s powered up and the thermostat is properly set to “Cool,” it’s still possible that the desired temperature setting got pushed way up, somehow (maybe somebody in the house felt too chilly.) Verify that the present thermostat temperature setting matches what you want. If it doesn’t, adjust accordingly.

Check the air filter.

A dirty, clogged air filter can reduce system airflow so much that the evaporator coil no longer extracts heat. Warm air from the vents is the result. If the filter looks dirty, change it and see if cooling performance improves.

Is the outside unit running?

Central air conditioners incorporate two circuit breakers. One controls power to indoor components including the system blower while the other controls outdoor components such as the system compressor. If the outdoor breaker trips due to some electrical issue, the compressor shuts down. Meanwhile, the indoor blower still runs but now circulates warm air. Because dangerously high voltages are involved, you need a service call from a qualified HVAC technician to sort this out.

Maybe there’s a refrigerant leak.

Refrigerant circulating between the indoor and outdoor coils extracts heat. If the amount of refrigerant in the system drops below specs—almost always because of a leak somewhere—the system cannot extract enough heat to cool the house. The result: warm air blows from the vents. A service technician can perform leak detection to pinpoint the issue, repair the leak, and restore refrigerant charge to specifications.

Standing by with solutions to issues like unresponsive HVAC settings, Paitson Bros. has been your local source for qualified professional service since 1922.

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