A heat pump that stops heating or cooling is more than an inconvenience. For a home depending on it through a humid Bangalore summer or a cold December night in Pune, every hour without it matters.
But before you call a technician or start pricing replacement units, it is worth knowing that most heat pump failures are not catastrophic. The overwhelming majority of performance problems trace back to a handful of causes that repeat across almost every installation, regardless of brand, age, or system type.
As one of the established solar product dealers in India, Sun-AP Ecopower has diagnosed and resolved these exact issues across hundreds of homes, hotels, hospitals, and commercial setups across India. The patterns are consistent, and so are the solutions.
Here are the 10 most common reasons a heat pump stops heating or cooling, and exactly what to do about each one. You may find the answer before you even pick up the phone.
1. The Thermostat Is Set Incorrectly
This sounds too simple to be the problem. It often is the problem.
If your thermostat is set to the wrong mode, fan-only instead of heating or cooling, or if the temperature is set lower than the room temperature in heating mode, the heat pump will run without actually conditioning the air.
What to do: Check that the thermostat is set to the correct mode, heating or cooling, and that the target temperature is actually higher or lower than the current room temperature depending on what you need. Also check that the batteries in your thermostat are not dead, since a low battery can cause erratic behaviour.
2. Dirty or Blocked Air Filters
A clogged air filter is one of the most common reasons heat pumps underperform. When the filter is blocked with dust and debris, airflow through the system is restricted. The heat pump cannot transfer heat efficiently, and in some cases the system will shut itself down to prevent overheating.
What to do: Check the air filter and clean or replace it. For most residential heat pumps, filters should be cleaned every 4 to 6 weeks depending on usage and environment. If your home is dusty or you have pets, check more frequently.
3. The Outdoor Unit Is Obstructed
The outdoor unit needs clear airflow around it to function properly. If plants, debris, furniture, or even a wall is too close to the unit, the heat pump cannot absorb or release heat effectively.
What to do: Check that there is at least 60 cm of clearance around all sides of the outdoor unit. Remove any leaves, dirt, or objects that may have accumulated around the unit. If the fins on the outdoor coil look bent or blocked with debris, have them professionally cleaned.
4. The Outdoor Unit Is Frozen Over
In cooler conditions, moisture in the air can freeze on the outdoor coil, forming a layer of ice that blocks heat absorption. Most modern heat pumps have a defrost cycle that handles this automatically. However, if the defrost cycle is malfunctioning or the ice buildup is excessive, the system will stop heating.
What to do: Check the outdoor unit for visible ice buildup. A light frost is normal, but a thick layer of ice covering the entire coil is not. Switch the system to fan-only mode for 30 to 60 minutes to allow it to defrost, then restart in heating mode. If icing continues to occur, the defrost sensor or control board may need professional attention.
5. Low Refrigerant Level
Refrigerant is the fluid that carries heat through the heat pump system. If the refrigerant level drops due to a leak, the system loses its ability to transfer heat effectively. This results in weak heating or cooling output, and the system may run continuously without reaching the target temperature.
Low refrigerant is one of the signs that often gets misread as a failing unit, but it is usually a fixable issue once the leak is identified and sealed.
What to do: This is not a DIY fix. If you suspect low refrigerant, contact a qualified technician. They will check the refrigerant pressure, locate any leaks, seal them, and recharge the system to the correct level.
If you are considering a more energy-efficient setup altogether, pairing your system with a solar heat pump reduces overall operating load and can extend the life of refrigerant components by reducing the number of operating cycles.
6. Electrical Issues or Tripped Breaker
A heat pump draws significant power, especially the compressor. If there is a voltage fluctuation, a short circuit, or an overload on the electrical circuit, the breaker may trip and cut power to the outdoor unit, the indoor unit, or both.
What to do: Check your electrical panel for any tripped breakers related to the heat pump. If a breaker has tripped, reset it once. If it trips again immediately, do not reset it a second time. A repeatedly tripping breaker indicates an underlying electrical fault that needs professional diagnosis.
Homes with solar setups should also check whether their solar inverter is supplying stable power to the heat pump circuit, especially if the system runs on solar-powered electricity during the day.
7. The Reversing Valve Has Failed
The reversing valve is what allows a heat pump to switch between heating and cooling mode by changing the direction of refrigerant flow. If this valve fails or gets stuck, the system may be locked in one mode regardless of what the thermostat says, or it may not condition the air at all.
What to do: Signs of a faulty reversing valve include the system only heating when you want cooling, or only cooling when you want heating. This is a component-level repair that requires a qualified technician to diagnose and replace.
8. The Compressor Is Not Running
The compressor is the core of the heat pump system. It pressurises the refrigerant and drives the entire heating and cooling cycle. If the compressor is not running, the system may still blow air but will not heat or cool it.
A compressor can fail due to electrical issues, overheating, refrigerant problems, or simply reaching the end of its operational life.
What to do: If the outdoor unit fan is running but you can hear no compressor noise or feel no temperature change, the compressor may have failed. This requires a professional assessment. Depending on the age and condition of the unit, repair or full replacement may be recommended.
9. Incorrect System Sizing
A heat pump that is too small for the space it is serving will run constantly and still fail to reach the target temperature. One that is too large will cycle on and off too frequently, which causes wear and reduces efficiency over time. Both scenarios result in poor heating and cooling performance that no amount of maintenance will fully fix.
This is a common issue when heat pumps are installed without a proper load calculation for the space.
What to do: If your heat pump has never performed well since installation, sizing may be the root cause. Sun-AP Ecopower, one of the leading solar heat pump distributors in India, provides pre-installation assessments to ensure the right capacity system is matched to your specific space and usage requirements.
10. Age and Wear
Heat pumps have a typical operational life of 10 to 15 years. As the system ages, components like the compressor, capacitors, and sensors begin to wear. Performance gradually declines, and the system may start struggling to reach target temperatures even though no single component has completely failed.
If your heat pump is more than 10 years old and showing consistent performance issues despite regular maintenance, age-related wear is likely a contributing factor.
What to do: Have a technician do a full system inspection. In many cases, replacing a few worn components can restore performance for several more years. If the system is over 12 to 15 years old with multiple failing parts, replacement with a newer, more efficient model is often the smarter financial decision.
Modern solar heat pump systems available today are significantly more efficient than units from a decade ago and can be paired with your existing solar setup to reduce running costs further. Read our guide on backup power planning with solar systems to understand how to build a more resilient energy setup for your home.
Quick Diagnosis Summary
| Symptom | Most Likely Cause |
|---|---|
| Blowing air but no heating or cooling | Thermostat setting, reversing valve, refrigerant |
| Weak output despite running continuously | Dirty filter, blocked outdoor unit, low refrigerant |
| System not turning on at all | Tripped breaker, electrical fault |
| Ice on outdoor unit | Defrost cycle failure, low refrigerant |
| Works in one mode only | Faulty reversing valve |
| Never performed well since install | Incorrect sizing |
| Gradually worsening over time | Age and component wear |
Frequently Asked Questions
Why is my heat pump running but not heating?
The most common reasons are a dirty air filter restricting airflow, low refrigerant levels, a faulty reversing valve, or an incorrect thermostat setting. Check the thermostat and filter first before calling a technician.
Can a heat pump stop working in cold weather?
A heat pump can struggle in very cold conditions if the outdoor unit ices over or the refrigerant level is low. For most Indian climates, cold weather is rarely the root cause. Check the outdoor unit for ice and ensure the defrost cycle is functioning correctly.
How often should a heat pump be serviced?
A heat pump should be professionally serviced at least once a year. Filters should be cleaned every 4 to 6 weeks depending on usage.
Is it worth repairing an old heat pump?
If the system is under 10 years old and the repair involves a single component, repair is usually worth it. If it is over 12 years old with multiple issues, replacement with a more efficient model is often more cost-effective in the long run.
How do I know if my heat pump refrigerant is low?
Signs include the system running continuously without reaching the target temperature, ice forming on the outdoor unit, or a noticeable drop in heating or cooling output. A technician will need to check refrigerant pressure to confirm.
Can I connect a heat pump to a solar system?
Yes. Heat pumps work very well with solar setups. When connected through a solar inverter, the compressor can run on solar power during the day, significantly reducing electricity costs. For homes looking to maximise energy independence, pairing a heat pump with solar is one of the most effective upgrades available through trusted solar product dealers in India like Sun-AP Ecopower.
