My Heat Pump Isn’t Heating: What’s Wrong With It?

Is your heat pump not heating? In most cases the cause is on a short list: a thermostat setting, a dirty air filter, low refrigerant, an electrical part, or a normal defrost cycle. Below, we walk through the most common heat pump problems, which ones you can safely fix yourself, and when it is time to call a professional. Because San Diego’s climate is mild, a heat pump here often doubles as both your heater and your central air conditioner, so keeping it healthy matters year-round.

Cost Key:

$ – DIY
$$ – low $100’s
$$$ – high $100’s to low $1,000
$$$$ – many $1,000’s/full replacement

Heat pumps can be a great choice for HVAC system, especially if you live in a milder climate where your heat pump might be able to double as your heater/furnace and your central air conditioning system.

Like any HVAC solution however, they can be prone to problems and benefit from routine maintenance just like your furnace or your air conditioner would.

In order to keep your system running smoothly, it’s important to keep an eye out for some common heat pump problems these types of HVAC solutions can experience. This way, you can be prepared to either fix it yourself if you can, or call in the professionals when you can’t.

Perhaps the number one heat pump complaint comes from the unit simply not turning on. This gets tricky because there can be a variety of reasons your heat pump may not be coming on. For example, it could be something as simple as your home’s thermostat not being set correctly, or not being properly calibrated for the temperature in your home. In these cases, it’s pretty simple to spot the problem yourself and correct it.

If, however, it’s something more serious like a bad starter capacitor, you’ll need an experienced HVAC professional’s help to fix it. You can generally tell if it’s the capacitor by listening to the heat pump itself — typically if you hear a faint clicking when it should be running, that’s the capacitor not getting the electrical charge to the motor correctly.

Heat pumps can be prone to problems in cold weather, and people often notice heat pumps running more often than a furnace would, especially in colder-than-normal temperatures. The fact that it’s running often during the winter isn’t inherently a problem. Complicating the matter however is that it could be a sign of low or leaking refrigerant, or that there could be a blockage around the outdoor unit.

You can do a visual inspection to look for leaves, debris, or icing over on the unit and this may give you some indication if you’re dealing with the latter of these problems. If you clear away the ice and still experience the perpetual running, it may be a problem with a bad compressor, which you’ll want a technician to take a look. Low or leaking refrigerant can also cause the unit to run irregularly and stop working effectively. This is another situation where you’ll want to have a technician service your unit to make sure you don’t have a serious refrigerant leak or more complicated heat pump problem.

Since heat pumps act similarly to central air units in the summer months, some of the more common issues with heat pumps overlap central air issues, like thermostat problems. Some however, are uniquely the domain of heat pumps, like broken reversing valves. If these valves are broken or malfunctioning for example, they can cause hot air to blow when the unit is set to cool. In this case, it’s best to have an experienced technician evaluate the problem and recommend solutions for you.

Refrigerant levels can also cause your heat pump problems in hot weather — just as it would in the colder months, if refrigerant is low or leaking, the unit will struggle to produce cool air for the home efficiently. A heat pump’s bad compressor can also be to blame if your unit seems to be running more than normal during the summer. Again, you’ll want to have an HVAC professional take a look to diagnose the problem and recommend the right solutions for your home and your cooling, and heating, needs.

Looking for more details about heat pumps? Visit our resource center to find more information about everything HVAC and more, or call our professionals at (619) 762-3044 today to see how we can help.

Use this quick reference to match what your heat pump is doing to the most likely cause, and to see what you can safely try yourself versus when to call a professional.

In moderate temperatures San Diego experiences throughout the year, electric might be the best option. It operates at the highest efficiency, and offers the lowest installation costs. Since nowhere in San Diego dips below freezing, heat pumps are rarely limited in their effectiveness by climate.

You can DIY common issues for an outdoor unit that is not running. This includes a thermostat not being set properly, an emergency shut-off switch or blown fuse/circuit breaker. Check your condensate pump to make sure it’s not unplugged.

However, issues that might require a service call include a broken contactor/capacitor, control module, bad cable/wiring or a faulty relay.

Cost: $-$$

Blown fuses and improperly functioning thermostats can be DIY fixed, however, many of the other fixes can range in the low- to mid-hundreds.

 Thermostat malfunctions are a common cause of heat pump issues. To just make sure it’s sending a signal, set it at 5 degrees higher than your typical setting. Make sure your wires are properly mounted on their respective screws. 

If your heat pump is covered in ice, shut it down! A couple things you can do on your own include:

Cost To Repair Frozen Heat Pump: $-$$

Typically, a frozen heat pump is due to external factors. A simple air filter change or gutter cleaning could free up the flow of air. Adding refrigerant or replacing a defrost timer can be a tad more expensive, but it shouldn’t break your bank.

This is likely an issue with the limit switch located below the plenum (the box that gives heat to your duct system), or a thermostat problem. You can change your heat pump limit switch, which is designed to shut off when the plenum gets too hot.

See your instruction manual for details or make a service call to reset the pointers on the fan side of the limit control.

If the blower motor is running but there’s no air, you probably have a belt issue.

Cost To Repair Heat Pump Blower: $-$$

A fan limit switch or thermostat typically cost under $100.

Heat pump issues? One of the first things you should check is your thermostat.

Your outside unit may be overheating. Check your air filters and thermostat. It is possible your thermostat isn’t properly calibrated or has been placed too close or far from a heat source.

Cost: $-$$$$

An overheating unit could require a replacement, however, a simple thermostat fix can be taken care of quite easily. 

Squealing/Grinding Noise – you might have an issue with the motor bearings. This isn’t a DIY fix. Call us!

Rattling – your heat pump’s cover panel might be loose, or your ductwork isn’t well connected. This might be a DIY fix, depending on where your loose ductwork is located. Knowing where to find it might require an expert, though. It depends on how long you’ve lived in your home, and how well you know the layout. 

Popping Noise – this sound is possibly expansion from your ductwork. This sound can be very common, especially in cold months when pressure contracts your ducts. It’s likely not a major issue, but check with your local HVAC contractor to make sure. Each home is structurally different. 

Cost: $-$$$

Simple noises don’t always require an immediate fix. But if you are in need of new ductwork, you could be facing an expensive project – up to $55/linear foot. 

Here’s something to think about. Maybe you could get away for a year without changing the oil on your car. 

But would you pay a couple hundred dollars annually to ensure that car lasted an extra three, five, or even seven years? The eventual thousands you’d save on major repairs, or purchasing a new vehicle years earlier than you’d prefer, more than balance the short-term spend. 

Looking for another resource? Check out this informative article here.

A heat pump blowing cool air in heat mode is usually one of three things. The most common and least worrying is a defrost cycle: in cooler weather the system briefly reverses to melt frost off the outdoor coil, and warm air returns on its own within a few minutes. If the cold air continues, the likely causes are low or leaking refrigerant or a malfunctioning reversing valve, the component that switches the unit between heating and cooling. Before calling for service, confirm the thermostat is set to heat and replace a dirty air filter, since restricted airflow can mimic the same symptom. If none of that fixes it, have a technician check the refrigerant and reversing valve.

One of the most common issues that can lead to heat pump malfunctions is dirty air filters. When an air filter becomes clogged with dirt, dust, and debris, it restricts airflow to the indoor unit, causing the heat pump to work harder than necessary. This not only reduces efficiency but can also result in overheating and damage to essential components like the blower motor. To avoid this problem, make sure to check and replace your air filters regularly, especially during peak heating and cooling seasons. Clean air filters can also help lower your energy bills by ensuring the system operates efficiently.

When the weather gets particularly cold, your heat pump may enter defrost mode to prevent ice buildup on the outdoor coil. This is a normal process that helps keep the unit running smoothly. However, if the defrost cycles become too frequent, it could indicate an issue with the evaporator coil or dirty coils, which can impede heat transfer. During defrost mode, you may also notice that your system activates auxiliary heat or emergency heat to maintain indoor comfort. If you suspect an issue with the defrost function or auxiliary heat, consider scheduling regular maintenance to ensure your system is running optimally.

If your heat pump suddenly stops working, one of the first places to check is your electrical panel. Circuit breakers can trip due to electrical overloads or faulty wiring, preventing the system from receiving the power it needs to function. Additionally, issues with the power switch or a malfunctioning starter capacitor can cause the unit to fail. Inspect the power supply to ensure everything is connected properly and check for blown fuses. If electrical problems persist, it’s best to call a professional for heat pump troubleshooting steps to avoid further damage to your system.

Low refrigerant levels are a common cause of heat pump issues, especially in extreme weather conditions. If you hear hissing sounds coming from your system, it may indicate a refrigerant leak. This not only affects your heat pump’s ability to produce warm or cool air but can also lead to increased energy bills as the system works harder to compensate. Leaks are typically caused by damage to the coils or faulty valves, and they require professional heat pump repair services to resolve. If left unchecked, refrigerant leaks can result in more extensive and costly repairs down the line.

If the fan is running but the air is not warm, start with the easy checks: make sure the thermostat is set to heat and above room temperature, and replace the air filter if it is dirty. When those are fine, the usual culprits are low refrigerant or a stuck reversing valve, the part that switches your heat pump between heating and cooling. Both require a licensed technician, since refrigerant work is regulated and a faulty valve needs diagnosis.

Emergency heat is a backup heating element that runs when your heat pump cannot keep up or has stopped working. In San Diego’s mild climate you rarely need it, so if your system switches to emergency heat on a normal day, that is a sign something is wrong. Use it only as a short-term bridge to stay warm, then schedule a diagnostic, because running emergency heat for long stretches uses far more energy.

Turn the thermostat to off, then switch the heat pump off at the breaker for about 60 seconds and back on. Wait a few minutes before setting the thermostat back to heat, since many units have a built-in delay that protects the compressor. If it still does not run after a reset, a tripped breaker or a control board issue may be to blame and is worth a professional look.

A well-maintained heat pump typically lasts about 10 to 15 years. Because San Diego heat pumps often run year-round for both heating and cooling, annual maintenance matters: clean filters, clear coils, and correct refrigerant levels are what keep a unit near the top of that range.

Some longer run times are normal, especially during a cold snap, because a heat pump warms a home gradually rather than in short bursts. Constant running paired with weak heat, rising energy bills, or short cycling is not normal and usually points to a dirty filter, low refrigerant, or a sizing problem worth having checked.

Preventing common heat pump problems often boils down to ensuring your system receives regular maintenance. By scheduling annual check-ups, you can address issues like dirty filters, worn-out components, and potential refrigerant leaks before they escalate. Regular cleaning of the indoor coil, outdoor coil, and ensuring proper airflow through the system can significantly extend the life of your heat pump. Staying proactive with maintenance will not only save you money on heat pump repairs but will also keep your system running efficiently year-round.

Most heat pump trouble traces back to a few culprits: a thermostat setting, a dirty filter, low refrigerant, or a worn electrical part. Simple fixes like resetting the thermostat, replacing a clogged filter, or clearing debris from the outdoor unit are safe to try yourself. Anything involving refrigerant, the compressor, the reversing valve, or wiring is a job for a licensed technician. If your heat pump still is not heating or cooling the way it should after the basics, do not wait for a small issue to turn into a costly one. Same Day’s San Diego technicians can pinpoint the problem fast and get your system back to keeping you comfortable. Call (619) 762-3044 or schedule a heat pump diagnostic online today.