What Is a Compressor?

A basic compressor definition is that it’s a mechanical device that increases the pressure of a gas or air by decreasing its volume. An HVAC compressor is a vital component in your cooling system.

An HVAC compressor is either an AC compressor or a heat pump compressor. Most people call them air conditioner compressors or air conditioning compressors, but in reality, the compressor in your heat pump (HP) is virtually identical. All Trane heat pumps and AC units use the patented Climatuff™ compressor.

What does a compressor do?

Your heat pump or AC compressor is the lifeblood of your outdoor unit. The compressor is responsible for circulating and pressurizing the refrigerant in your unit, so the refrigerant can carry and release heat. If refrigerant didn’t move throughout your unit and release heat, cold air wouldn’t be produced and your home would remain warm. This means, that without the compressor, your unit wouldn’t be able to function.

Refrigerant is a cooling compound that absorbs heat and humidity from your home, carries it, and then releases that heat and humidity outside to ultimately cool your home. In heating mode, a heat pump reverses the refrigeration cycle to transfer outdoor heat energy into your home. But, the refrigerant can’t do its job without the compressor.

Refrigerant changes from liquid to gas during its journey through the air conditioner, but when it reaches the compressor, it is in gaseous form. The compressor applies energy to the gaseous refrigerant or compresses it, so it becomes a high-pressure gas. The compressor also raises the temperature of the refrigerant, so that it’s hotter than the temperature outside. 

Once the compressor performs these two tasks on the refrigerant, the refrigerant is forced into the condenser coil. Here, it can release all the heat and humidity it’s carrying outside and turn back into a liquid.

Signs of a failing heat pump or AC compressor

Your HVAC compressor is one of the hardest working parts of your AC system or heat pump system. All that wear and tear can lead to an eventual breakdown. You should know a compressor can also be one of the most expensive parts to replace. 

If your air conditioner compressor fails, your entire air conditioning unit will fail, resulting in the need for AC troubleshooting. An HVAC compressor carries a high voltage so improper handling can result in serious injury or death. Therefore a licensed HVAC technician is the only person to inspect and service a broken compressor. But there are some warning signs of compressor failure, including, but not limited to:

• Unchanging temperatures in your home: If your AC or heat pump is on, but the temperature in your home isn’t going down, (or up if the HP is in heating mode) the compressor might not be working properly. 
• Lukewarm or cool air is being released outside during hotter months. When it’s functioning properly, it should be releasing hot air outside. To detect whether your unit is releasing hot air, go outside while your heat pump is in cooling mode or your air conditioner is turned on. 

Without getting too close to your unit, stand near the outdoor fan. Without actually touching the unit, align your hand with the fan. You should be able to feel a stream of hot air coming out of the unit. If you feel lukewarm or cold air coming from the unit in the summer, your compressor might not be working. 

• Strange noises coming from your AC or heat pump: When your unit is turned on and functioning properly, you should hear the fan and compressor running smoothly, with a slight hum. If you hear banging, hissing, clattering, or screeching noises, it’s likely that your compressor or another HVAC component is not working properly and you need to call an HVAC professional.
• Leaks around your unit: If you go outside and see a leak around your air conditioner or heat pump, do not go near it. This may be a refrigerant leak, which is a sign that some part of the cooling cycle, possibly the compressor, is not working as it should. Refrigerant is a dangerous chemical, and should only be handled by an HVAC professional.

Heat pump or AC compressor replacement: What to consider

If you suspect that your heat pump or AC compressor might be failing, you’re likely wondering if you should repair or replace the unit altogether. The first step in this process is to bring in an HVAC contractor to ensure it’s your compressor that has failed and that no other parts of your air conditioning system or heat pump system are causing issues. 

After that, here are some things you should consider when you’re thinking about whether you should repair your air conditioner compressor or replace the entire unit:

• How long you’ve had the unit and if it is nearly time for a new one (AC and heat pumps have an average life expectancy of 10-15 years)
• If your unit is under warranty for replacement parts
• The cost of replacing the HVAC compressor vs. replacing the entire unit

Check out our Repair or Replace Guide to help you make this important decision.

Heat pump/AC compressor replacement cost

How much it costs to replace your heat pump or AC compressor depends largely on whether your unit is under warranty or not. If your unit is under warranty, the cost of the compressor itself would likely be covered, but you would be responsible for labor costs.

If it’s not under warranty the compressor replacement can cost anywhere between $900-$2,900, according to Forbes.

Keep in mind, that sometimes it might be more cost-effective to replace your unit entirely if your compressor doesn’t work, especially if your unit is not under warranty. Federal tax credits and heat pump rebates make now a more affordable time to upgrade your HVAC system. 

Heat pump and AC compressor maintenance

Compressor maintenance is NOT a DIY project.  Compressor maintenance should only be handled by an HVAC professional. The main things you can do yourself to maintain your heat pump or AC unit are to make sure nothing is on top of or blocking the unit that might restrict airflow, and to regularly change your air filters.Beyond that, heat pump or air conditioner maintenance is to be handled by an HVAC professional. When your technician services your unit, they’ll make sure your compressor and the rest of your unit is running properly. They’ll also clean your condenser coil, which works hand in hand with the compressor to release hot air. With proper maintenance, the HVAC compressor can last up to 15 years!