Heat Pump Guide
Heat Pump Not Heating? 8 Common Problems and What They Mean
Some causes are simple fixes; others need a pro. Here are the eight most common reasons a heat pump stops heating.
When your heat pump stops putting out heat on a cold Maine day, it’s stressful. The good news: some causes are simple, and knowing what’s going on helps you decide when to call a pro.
1. It’s in defrost mode (this one’s normal)
In cold weather, heat pumps periodically run a short defrost cycle to melt frost off the outdoor coil. During it, the unit may blow cool air for a few minutes and you might see steam outside. This is normal — wait 10–15 minutes and heating should resume.
2. Dirty filters or coils
A clogged filter or grimy indoor coil chokes airflow, so the system can’t move heat into your rooms. Check and clean the filters first — it’s the most common and most fixable cause of weak heating.
3. The outdoor unit is blocked by snow or ice
Heavy snow, ice buildup, or leaves around the outdoor unit stop it from pulling in air. Gently clear snow and debris — never chip at ice with sharp tools. If it keeps icing over, that points to a deeper issue worth a service call.
4. Wrong thermostat or remote setting
It happens more than you’d think: the unit is set to cool, fan, or dry instead of heat, or the temperature is set too low. Double-check the mode and setpoint on your remote or thermostat.
5. Low refrigerant
If refrigerant is low — usually from a leak — the system loses its ability to move heat and blows lukewarm air. This is not a DIY fix; it requires a licensed technician to find the leak and recharge the system.
6. A tripped breaker or power issue
If the outdoor unit is completely dead, check your breaker panel. A repeatedly tripping breaker is a sign of an electrical problem that needs professional diagnosis — don’t just keep resetting it.
7. A failing capacitor, compressor, or reversing valve
These internal components are the heart of the system. A bad reversing valve can leave a unit stuck in cooling mode; a weak compressor or capacitor can kill heat output. These require a technician.
8. It’s simply overdue for service
Sometimes “not heating well” isn’t a breakdown — it’s the slow decline of a system that hasn’t been cleaned in years. A thorough service often restores heat output owners assumed was gone for good.
What you can safely check yourself
• Set it to Heat and raise the temperature
• Clean the filters
• Clear snow and ice from the outdoor unit
• Wait out a defrost cycle (10–15 minutes)
• Check the breaker
If it’s still not heating after those, it’s time to call a professional — especially for anything involving refrigerant, electrical, or internal parts.
• Clean the filters
• Clear snow and ice from the outdoor unit
• Wait out a defrost cycle (10–15 minutes)
• Check the breaker
If it’s still not heating after those, it’s time to call a professional — especially for anything involving refrigerant, electrical, or internal parts.
Frequently Asked Questions
Why is my heat pump blowing cold air?
Most often it’s a defrost cycle (normal), a wrong mode setting, dirty filters, or low refrigerant. Check the easy ones first.
Why is my heat pump running but not heating the house?
Usually restricted airflow from dirty filters or coils, a blocked outdoor unit, low refrigerant, or a failing internal component.
Is no heat an emergency?
If you have no heat in freezing weather and the basic checks don’t fix it, call for service promptly to avoid frozen pipes and discomfort.
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Just Maintain ME provides fast, knowledgeable heat pump repair across central Maine. Call (207) 250-2300 or request service online.
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