Heat pumps & ductless
Heat pump repair
A heat pump that blows cool air, stays iced over or leans on auxiliary heat usually has a defrost-control problem, a stuck reversing valve, low refrigerant or a failed outdoor fan or capacitor. Some frost and short defrost cycles in winter are normal; a solid block of ice is not.
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- Diagnosis and price before work
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In heating mode a heat pump's outdoor coil runs cold, so frost forms in damp weather. Every so often it reverses briefly to melt it, which can puff steam and make a whooshing sound. That's normal. A unit encased in ice for hours needs service.
The thermostat's "aux" or "emergency heat" setting uses electric strips or a furnace. Running on it for long periods works in a pinch, but it costs far more than normal heat-pump operation.
Heat Pump Repair at a glance
- Category
- Heat pumps & ductless
- Urgent service
- Often available, depending on local contractors
- Who does the work
- An independent, licensed HVAC contractor
- Quote
- Given after diagnosis, before work starts
Signs you need heat pump repair
- Outdoor unit covered in ice that doesn't clear
- Lukewarm air in heat mode
- Auxiliary heat light on constantly
- Won't switch between heating and cooling
- Loud buzzing or grinding outside
What the technician does
- 1
Mode and controls
Thermostat settings, defrost board and sensors checked first.
- 2
Reversing valve and fan
Valve solenoid and coil temperatures tested; outdoor fan motor and capacitor measured.
- 3
Refrigerant
Charge checked in the current mode; leaks located rather than topped off.
- 4
Verify both modes
Heating and cooling run and switch correctly before the visit ends.
What affects the cost
Prices are set by the contractor after diagnosis. These are the factors that move the number most:
- Failed part: capacitor and defrost sensor vs. reversing valve or compressor
- Refrigerant type and leak repair
- System age
- Access to outdoor and indoor units
Safe to check yourself
- Clear snow and ice around the base so it can drain
- Replace the filter
- Confirm the thermostat is in heat, not cool or off
Leave to a pro
- Chipping ice off the coil
- Pouring hot water on the outdoor unit
- Opening electrical panels
Heat Pump Repair FAQ
Is it normal for a heat pump to blow cool air in winter?
During a short defrost cycle, yes; it lasts a few minutes. If air feels cool for long periods, the unit may be low on refrigerant or stuck in the wrong mode.
Why is my heat pump running all the time?
In very cold weather a heat pump runs long cycles by design. Constant running in mild weather points to low refrigerant, a dirty coil or a sizing problem.
Should I use emergency heat?
Only when the heat pump has failed or is iced solid. It keeps the house warm but costs much more to run, so schedule a repair soon.
What is defrost mode?
Defrost mode briefly reverses a heat pump to melt frost on the outdoor coil in cold, damp weather. It lasts a few minutes and may release steam; it's normal.
Why is my heat pump blowing cold air in heating mode?
During defrost, briefly, that's normal. If it lasts, the reversing valve may be stuck, the unit may be low on refrigerant, or the thermostat may be set up for the wrong system type.
What does the 'aux heat' light mean?
It means backup heat, usually electric strips or a furnace, is running alongside the heat pump. That's normal in very cold weather or during defrost, but constant aux heat in mild weather points to a problem.
How long do heat pumps last?
Most heat pumps last 12–15 years. Because they run in both seasons, regular maintenance has a big effect on lifespan.
Can a heat pump freeze up in summer?
Yes, the indoor coil can ice in cooling mode from low airflow or low refrigerant, just like an air conditioner. Turn it off and let it thaw, then have the cause found.
Last reviewed . General information, not a diagnosis of your system.
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