Heat Pump Not Heating? Here’s How to Troubleshoot

If your heat pump is running but not heating, the issue is often simple to fix, like an incorrect thermostat setting or a dirty air filter. However, if the system is blowing cold air constantly or the outdoor unit is frozen, it may indicate a refrigerant leak or a faulty reversing valve requiring professional repair from  your local Carrier dealer.

Troubleshooting: Heat Pump Not Heating

Before calling a professional, try these homeowner-friendly troubleshooting steps. Knowing a little about how a heat pump works is important, because the heat pump could be functioning normally even though you are not currently comfortable.

1. Check Thermostat Settings

Incorrect thermostat settings: If you feel cool air coming from the registers, first check if your thermostat is set to "heat." If it is set to "cool" or "constant fan," the heat pump blowing cold air is a result of those settings. Switch it back to heat. Note that air from a heat pump register may naturally feel cooler than the intense heat from a gas furnace.

Uncalibrated or faulty thermostat: If the room temperature doesn't match the setting, the thermostat might be uncalibrated due to dirt or accidental bumps. Consult your user manual to recalibrate it.

2. Inspect Power Sources

Circuit breaker is tripped: If the heat pump isn't running at all, check your electrical panel. The outdoor unit (usually on a 220v or 240v breaker) and the indoor unit have separate breakers. Reset them if tripped. If they keep tripping, call a professional.

Outdoor/Indoor power switches: Ensure the dedicated power disconnect switch near your outdoor unit and the power switch on your indoor air handler (which looks like a light switch) are both in the "on" position.

3. Examine Airflow and Filters

Dirty air filter: A clogged filter restricts airflow, potentially causing the system to shut down or blow lukewarm air. Locate your filter near the indoor unit and clean or replace it. For detailed steps, visit our guide on how to change a filter.

Leaking duct: If airflow is weak and energy bills are rising, you might have leaky ducts. While you can check exposed ducts for leaks by hand, most ductwork is hidden and requires an HVAC contractor to properly diagnose.

4. Check the Outdoor Unit

Frozen outdoor unit: If ice builds up on the outdoor coil or copper tubing, the system cannot transfer heat into your home. While a light frost that melts during defrost mode is normal, thick ice indicates an issue like low airflow or low refrigerant. See our article on will a frozen AC fix itself? for more details.

Blocked outdoor coil: Debris like leaves or cottonwood can clog the outdoor coil, reducing efficiency. Ensure the unit is clear of obstructions.

5. Signs You Need a Professional

Low refrigerant charge: If the heat pump can't keep up with demand or the coil is frozen, you might be low on AC refrigerant. A Carrier dealer can check the charge and repair leaks.

Bad reversing valve: If you have a heat pump not heating, but it works perfectly in cooling mode, the reversing valve—which switches the direction of refrigerant flow—may be stuck. This requires a local Carrier expert.

Curtis Herchenbach, owner of Herchenbach Mechanical in Gurnee, IL, offers guidance on what homeowners can check themselves versus leave to a professional.

Heat Pump Not Working in Cold Weather

Heat pumps naturally lose some efficiency as temperatures drop below freezing. If your home feels cold, your system might be relying on a supplemental heat source, like electric resistance strips or a gas furnace.

If the outdoor unit isn't working, you can switch to "emergency heat" on your thermostat to use this supplemental source. However, use this sparingly, as relying solely on electric resistance heat can significantly increase your electric bill.

Heat Pump Not Cooling in Summer

If your heat pump isn't cooling effectively during summer, the troubleshooting steps are similar:

• Thermostat: Ensure it is set to "cool" or "auto" and the temperature is set lower than the room temperature.

• Power: Check breakers and power switches.

• Air Filter: Replace your air filter if it is dirty.

• Outdoor Unit: Clear away debris and check if the unit is running.

If these quick fixes don't resolve the heat pump not cooling, contact a professional for heat pump repairs.

When to Call an Expert

While simple fixes like changing filters or adjusting thermostats are easy DIY tasks, complex issues involving refrigerants or electrical components require a professional. We recommend scheduling a heat pump service appointment with a qualified Carrier HVAC dealer to protect your investment and ensure long-term comfort.