A heat pump that keeps blowing air after reaching the desired temperature may not need a repair. As one Reddit discussion showed, the solution could be an installer setting, depending on the equipment and its configuration.

Here's what to know

A 68-degree thermostat setting wasn't keeping one homeowner's room from reaching 70 degrees, with warm air still flowing. The owner, who had two Hyperheat units, asked about the behavior in r/HeatPumps on Reddit.

"Why do my Mitsubishi heat pumps continue to run on AUTO setting?" the original poster asked, adding that this happened "even when set temperature has been reached?"

One commenter noted, "The fan runs 24/7. When space is satisfied, the fan will go to extra low but keep running. When there is a call, the fan will run at the speed set on the controller. Are you sure the fan isn't just running but the unit is not actively heating?"

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More background

Another Mitsubishi heat pump owner described,  "I have the exact problem. Set the heat to 68, it gets up to 74-75 without turning off. Continuously runs. It's really frustrating. Would love to know what the fix actually is."

Commenters offered several possible explanations.

Some thermostat interfaces lack information about the thermostat's temperature reading and setpoint, relying instead on indoor-unit sensors, according to one reply. A separate commenter raised MHK2 thermostat modulation as a possible explanation.

For homeowners weighing an equipment upgrade rather than a settings adjustment, Palmetto's Comfort Plan includes $0-down options for those not ready to spend up front, with potential heating and cooling cost reductions of up to 50%. Palmetto Comfort Plans also include 12 years of free maintenance.

What can be done?

Heating and cooling have separate fan controls in the function menu — options 25 and 27, respectively — that one commenter said could stop airflow once the desired temperature is reached.

They suggested setting both options to 0, but added, "I see you don't have WiFi, you will have to search how to get into the settings menu on MHK2 and go to option 25 and 27 and set them to 0. I believe 0 maps to off."

Given that uncertainty, homeowners should check their model's manual or confirm the settings with an installer before making changes.

Another commenter recommended reviewing the installer settings, where the system can be configured to use the thermostat sensor, the return-air sensor, or both.

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Where can I learn more?

HVAC systems can sometimes leave homeowners unsure whether to adjust a setting or call for repairs.

• For an upstairs that became a sauna, commenters called Mitsubishi the 'gold standard.'

• A homeowner's aging furnace stopped running long cycles after a thermostat setting change.

• A Mid-Atlantic homeowner's soaring heat pump bill led commenters to flag 'luxury mode'.

• HVAC pros blamed a heat pump freeze-up on 62-degree operation and MERV 12 filtration.

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