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Heat pumps run on 240-volt circuits and contain capacitors that hold a lethal charge even after power is cut. The safest action for a homeowner is to set the thermostat to OFF (or Emergency Heat) and call a qualified HVAC technician. Do not kill the power by going to your service panel to flip the breaker yourself — the technician will handle the power-down and disconnect sequence on arrival. Refrigerant-side diagnosis is federally regulated under EPA Section 608, certification is legally required, and refrigerant work is never a homeowner task. Do not open the outdoor cabinet, touch the capacitor or reversing valve, chip ice off the coil, or pour water on the unit.
Heat pumps handle both heating and cooling, so a single component failure can disable both modes. Common causes of cold air in winter: failed reversing valve, low refrigerant, or frozen outdoor unit. Standard heat pumps lose efficiency below 35–40°F; cold-climate models work down to −13°F. Brief cool air during a 5–15 minute defrost cycle is normal — continuous cold air is not.
A heat pump is one of the most efficient ways to heat and cool a home — but because it handles both functions using the same refrigerant circuit and reverses direction between seasons, a single component failure can disable heating, cooling, or both. Diagnosing a heat pump problem is more complicated than diagnosing a furnace or a standard central AC because the symptoms often look the same but have different causes depending on the mode the system is in.
This guide separates heat mode failures from cool mode failures, explains what is normal behavior vs. a real problem, and gives you the actual repair cost data you need to make a smart decision.
How Does a Heat Pump Work?
A heat pump does not generate heat by burning fuel — it moves heat from one place to another. In summer, it works exactly like a central air conditioner: it absorbs heat from indoor air and dumps it outside. In winter, it reverses this process, extracting heat from outdoor air (even in cold weather, there is usable heat energy in outdoor air down to well below freezing) and moving it inside.
The component that makes this reversal possible is the reversing valve — a solenoid-controlled valve in the refrigerant line that redirects refrigerant flow between heating and cooling directions. When the reversing valve fails, the system gets stuck in one mode. This is one of the most common and most misunderstood heat pump failure modes.
Everything else in a heat pump — the compressor, capacitors, contactors, refrigerant circuit, and air handler — works essentially the same as a conventional split AC system. The diagnostic approach for those components is the same.
Why Is My Heat Pump Blowing Cold Air in Winter?
If your heat pump runs in winter but produces little or no warm air, work through the following causes in order — from most common and cheapest to fix, to least common and most expensive.
1. Clogged Air Filter
A dirty air filter restricts airflow across the evaporator coil. In heat mode, this limits how much heat the system can transfer to indoor air. The result: the air handler runs, air comes out, but it feels barely warm. Check the filter first. If it is gray and dense, replace it and run the system for 30 minutes before concluding there is a deeper problem.
2. Normal Defrost Cycle
In cold, humid weather, frost accumulates on the outdoor coil. The heat pump periodically enters a defrost cycle — it temporarily switches to cooling mode to melt the frost. During defrost (5–15 minutes), the indoor unit blows slightly cool air. This is normal and not a malfunction. See the defrost cycle section below for how to distinguish a normal defrost from an abnormal one.
3. Failed or Stuck Reversing Valve
The reversing valve is heat pump-specific. When it fails, the system can get stuck in cooling mode even when set to heat. Symptoms: the outdoor unit runs normally, but you feel cool or room-temperature air from the vents in heat mode. A technician confirms this with refrigerant pressure readings — the suction and discharge pressures in the lines will be reversed relative to what they should be in heat mode.
A reversing valve replacement costs $250—$600 in parts and labor. Some technicians can repair the solenoid that controls the valve ($100—$200) if the valve body itself is mechanically intact. On older systems, a failed reversing valve often prompts a repair-vs-replace decision because the component is labor-intensive to access.
4. Low Refrigerant
A refrigerant leak affects heat mode and cool mode equally — the system cannot move heat effectively in either direction. In winter, low refrigerant often shows up as ice accumulating on the outdoor unit that does not clear during defrost cycles. See our refrigerant leak guide for the full repair process and costs.
5. Outdoor Unit Frozen Solid
In very cold, wet weather, the outdoor unit can accumulate ice faster than the defrost cycle can clear it. A coil encased in thick ice cannot absorb heat from outdoor air. The system runs but produces no meaningful heat output. You may need to manually defrost the unit — turn the system to emergency heat or fan-only mode, wait for the ice to melt naturally (do not use sharp objects or a torch), and call a technician to inspect why the defrost cycle is not keeping up.
6. Thermostat Set to Emergency Heat
If someone has set the thermostat to "Emergency Heat" (or "Em Heat"), the heat pump is bypassed entirely and only the backup electric resistance strips or gas furnace runs. This can be correct in certain situations, but it uses significantly more energy and is not designed for continuous operation. Verify the thermostat is set to "Heat" mode, not "Em Heat."
In freezing weather, heat pumps can ice over — this is a known technician-handled problem. From inside the house or a safe distance, check whether the outdoor unit is visibly encased in ice. If it is, set the thermostat to emergency heat (or fan-only if there is no emergency heat option) and call a technician. Do not try to chip, spray, or physically clear ice from the unit, do not approach the unit to scrape snow off it, and do not open the cabinet to inspect anything inside. A technician will safely thaw the unit, identify why the defrost cycle failed, and restore normal operation.
Why Is My Heat Pump Blowing Warm Air in Summer?
In cooling mode, a heat pump behaves identically to a standard split AC system. All of the same failure modes apply:
- Failed run capacitor: The capacitor provides the electrical jolt that starts and runs the compressor and fan motors. A failed capacitor means the outdoor unit hums but does not start. Cost: $150—$350.
- Dirty condenser coil: The outdoor coil must be able to reject heat to the air. A coil packed with debris can only move heat inefficiently, reducing cooling capacity significantly.
- Low refrigerant: Same as in heat mode — the system cannot move heat in either direction when refrigerant is low.
- Failed compressor: The compressor is the heart of the refrigerant circuit. A failed compressor means no cooling (or heating). Cost: $1,000—$2,500. On systems older than 8–10 years, a failed compressor is typically the trigger for full system replacement.
- Stuck reversing valve: Can get stuck in heat mode, causing the system to try to heat when you have set it to cool.
If your heat pump provides adequate cooling in summer but struggles in winter (or vice versa), the reversing valve is the most likely culprit. If it struggles in both modes, focus on refrigerant level, compressor condition, or airflow issues.
Connect with a local independent HVAC technician for a heat pump diagnosis. Most problems can be identified and quoted in a single service call.
Call Now — (844) 582-1795Disclosure: We are a referral service and may receive compensation for qualified calls. Calls may be routed to an independent provider network and may be recorded. Pricing and availability vary by provider and location.
What Is the Heat Pump Defrost Cycle?
Many heat pump service calls are triggered by homeowners alarmed by something completely normal: the defrost cycle. Understanding what it looks like is the fastest way to avoid an unnecessary dispatch fee.
What Normal Defrost Looks Like
- The outdoor fan stops spinning (intentional — this prevents cold air from blowing across the coil during defrost)
- Steam or vapor rises from the outdoor unit as frost melts
- The indoor unit continues to run but blows slightly cooler air
- A rushing or hissing sound as the refrigerant direction reverses
- Duration: 5–15 minutes, then the system resumes normal heat mode
When Defrost Becomes a Problem
- Defrost runs for more than 20–30 minutes without the unit returning to heat mode
- Ice does not fully clear between defrost cycles, leaving the coil partially or fully encased
- Defrost cycles occur very frequently — every 30–60 minutes in conditions that are cold but not extreme
- No steam or ice clearing during the defrost cycle (may indicate the defrost board is triggering incorrectly, or refrigerant is too low to generate enough heat to melt the frost)
Abnormal defrost is typically caused by a defrost control board failure ($150—$400 to replace), a defrost sensor failure ($80—$200), low refrigerant, or a reversing valve that is not fully switching during defrost.
Do Heat Pumps Work in Cold Climates?
Standard heat pumps are rated for operation down to about 25–30°F outdoor temperature. Below that, the amount of heat energy available in outdoor air drops steeply, and the system's coefficient of performance (COP) — how many units of heat output it produces per unit of electricity consumed — falls below 1:1. At that point, resistance heating strips (electric backup heat) kick in automatically and are far less efficient.
If you live in a climate where temperatures regularly drop below 20°F and you are running a standard heat pump, reduced performance in severe cold is expected behavior, not a malfunction. The following table shows how different heat pump types perform across temperature ranges:
| Outdoor Temperature | Standard Heat Pump | Cold-Climate Heat Pump | Notes |
|---|---|---|---|
| 50°F+ | Excellent efficiency (COP 3–4) | Excellent efficiency (COP 3–5) | Peak operating range for both |
| 35–50°F | Good efficiency (COP 2–3) | Good to excellent (COP 2.5–4) | Defrost cycles begin |
| 20–35°F | Reduced efficiency (COP 1.5–2) | Good efficiency (COP 2–3) | Aux heat may supplement standard HP |
| 5–20°F | Aux heat dominates (COP ~1) | Moderate efficiency (COP 1.5–2.5) | Cold-climate HP still significantly better |
| Below 5°F | Aux heat only | Still operational (rated to -13°F to -22°F) | Cold-climate models (e.g., Mitsubishi H2i, Carrier Infinity) |
If your heat pump struggles in temperatures your area regularly experiences, and you have a standard (non-cold-climate) model, the correct solution may not be a repair — it may be upgrading to a cold-climate model or adding a dual-fuel backup.
How Much Does Heat Pump Repair Cost in 2026?
Repair costs depend on the part, its location in the system, your region, and whether the call is routine or emergency-dispatched. The ranges below reflect what most homeowners actually pay for a standard service call with a qualified independent HVAC technician.
| Problem | Typical Repair Cost | DIY Possible? | Notes |
|---|---|---|---|
| Air filter replacement | $5—$30 | Yes | Do this first before any other diagnosis |
| Thermostat replacement | $150—$400 | Partial | Smart thermostats require correct heat pump configuration |
| Defrost sensor replacement | $80—$200 | No | Labor is the main cost |
| Defrost control board | $150—$400 | No | Required when defrost fails to initiate correctly |
| Run capacitor | $150—$350 | No | Most common outdoor unit failure; inexpensive part |
| Contactor replacement | $100—$300 | No | Often done alongside capacitor |
| Reversing valve replacement | $250—$600 | No | Heat pump-specific; labor-intensive |
| Refrigerant recharge (+ leak repair) | $300—$800 | No | EPA 608 certification required; R-410A costs rising |
| Blower motor replacement | $300—$700 | No | Indoor or outdoor fan motor |
| Compressor replacement | $1,000—$2,500 | No | Often prompts full system replacement on older units |
| Full heat pump system replacement (2–3 ton) | $4,000—$9,000 | No | Includes air handler; cold-climate models at the high end |
| After-hours / emergency premium | +$75—$200 | ✓ | Added to any repair on evenings or weekends |
Should I Repair or Replace My Heat Pump?
Because heat pumps run year-round in many climates, they accumulate operating hours faster than a furnace or AC that only runs one season. A 12-year-old heat pump may have as many operating hours as a 20-year-old furnace. Use this framework:
Multiply the repair cost by the system age. If the result exceeds $5,000, replacement usually makes more financial sense. Example: a $600 reversing valve repair on a 6-year-old system = $3,600 — repair makes sense. A $1,800 compressor repair on a 12-year-old system = $21,600 — replacement makes more sense.
- System is under 8 years old: Repair nearly any problem except compressor failure. The system has significant remaining efficiency and service life.
- System is 8–12 years old: Repair moderate problems (capacitor, contactor, reversing valve, refrigerant recharge). Avoid expensive repairs like compressor replacement — the cost approaches replacement territory on a system of this age.
- System is 12+ years old: A compressor failure, a second refrigerant recharge, or any repair exceeding $1,000 is typically the tipping point for replacement. Modern ENERGY STAR-rated heat pumps under the current SEER2 / HSPF2 standards are substantially more efficient than units built 12+ years ago, and the energy savings often contribute meaningfully to payback on a new unit.
- Standard HP in a cold climate: If you have a standard (non-cold-climate) heat pump in a region with frequent sub-25°F winters and are considering replacement, prioritize a cold-climate model. The efficiency improvement in cold weather can be dramatic — lowering heating bills significantly compared to running auxiliary resistance heat through a cold winter.
See our full HVAC repair cost guide for a broader breakdown of repair vs. replacement costs across system types.
Connect with a local independent HVAC provider for a heat pump service call. Most diagnoses are completed in a single visit.
Call Now — (844) 582-1795Disclosure: We are a referral service and may receive compensation for qualified calls. Calls may be routed to an independent provider network and may be recorded. Pricing and availability vary by provider and location.
Frequently Asked Questions
The most common causes are: a failed reversing valve stuck in cooling mode, low refrigerant from a leak, a normal defrost cycle running (5–15 minutes of cooler air is expected), a dirty air filter restricting airflow, or an outdoor unit frozen solid due to ice accumulation. If the system blows cold air continuously in heat mode and is not in a defrost cycle, it requires professional diagnosis.
Standard heat pumps become significantly less efficient below 35–40°F and typically cannot provide adequate heat below 25–30°F without auxiliary heat. Modern cold-climate heat pumps are rated to operate efficiently down to -13°F to -22°F. If your heat pump struggles in cold weather and you do not have a cold-climate model, that is expected behavior for your equipment type — not necessarily a malfunction.
During defrost, the outdoor fan stops, steam may rise from the unit as frost melts, and you may feel slightly cooler air from indoor vents for 5–15 minutes. This is completely normal in cold, humid conditions. A defrost cycle running longer than 20–30 minutes, or ice that does not clear between cycles, is abnormal and warrants a service call.
In mild to moderate climates (rarely below 20°F in winter), a modern cold-climate heat pump can serve as a full heating and cooling system without a furnace. In colder climates, a dual-fuel system — heat pump plus gas furnace backup — is common. An all-electric heat pump can work in cold climates with the right model, but proper sizing and home insulation are critical to performance.
The typical lifespan is 15–20 years with proper maintenance. Because heat pumps run year-round in many climates, they accumulate more operating hours than seasonal equipment. Annual professional tune-ups, regular filter changes, and keeping the outdoor unit clear of debris are the most important factors in reaching the upper end of that range.
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