NewsHow to Troubleshoot and Fix a Faulty HVAC Compressor That Won't Turn...

How to Troubleshoot and Fix a Faulty HVAC Compressor That Won’t Turn On

Category articles

How to Fix the HVAC Compressor That Won’t Turn On?

An HVAC is a term used to describe Heating, Ventilation, as well as Air Conditioning equipment. all of them require the use of a compressor (just like the heart of our body) to ensure their proper functioning. It is commonplace that we locate the compressor whenever HVAC equipment isn’t working.

It’s a common occurrence that the compressor’s air supply has a higher chance to wear faster than other components in the machine. If something is wrong, or the compressor doesn’t turn on correctly, it can result in the unit becoming malfunctioning. It is essential to fix the mechanical issues which are hindering its operation and allow it to function properly in order for the HVAC equipment to function efficiently.

In this post, we’re offering a simple guideline to figure out what to do if the HVAC compressor isn’t working or is not turning on.

Before we get into the main subject Here is a brief description of an HVAC compressor.

HVAC Compressor

Most often, the compressor is located on the outside in the HVAC unit. The compressor compresses cold, low-pressure and gaseous refrigerant. It is it is then compressed into a condenser unit to transfer as a vapor from the outside unit and into the inside. This is because it absorbs warm air that is escaping through the vents, ensuring adequate cooling of the room and the heat is transferred between cool and warm zones.

To do this, it is important to keep the compressor in good functioning order. The compressors can last between 12 to 15 years. Certain indicators will indicate that the compressor isn’t functioning properly or has broken. Make use of a specific gauge or device to determine the precise component that is the HVAC unit, such as the AC is experiencing the problem.

The air compressor is composed up of various parts which are repaired separately, meaning it is possible to inspect, check and repair the specific component that is causing problems instead of replacing the whole compressor. Therefore, it can save lots of time and money in solving small problems in the compressor.

Why Won’t the AC Compressor Work Yet the Condenser Fan Runs?

Most of the time, the compressor will be unable to work due to different causes, even though the condenser and blower fans operates by pushing warm air through the vents. If your compressor isn’t functioning correctly, it is necessary to examine the causes issues and ways to identify them.

1. Overheating & Auto-Shut Down for Safety:

A compressor can become overheated when there’s inadequate coolant suction or cooling condenser since it can increase both temperature and pressure. It must work extremely all the time, and even operate for a long time without stopping. This causes it overheated, and shuts off quickly. As an example, operating temperature of an air conditioner can be between 50-450 PSI and, if the pressure is over or below this level it could shut off power to the compressor by itself.

2. System Contamination (or) Dirty Filter:

The dirty filters, or system contaminants such as acid, air dirt, and other contaminants, aside from pressure and heat could be the cause of this issue. If the condensers and filters of the air conditioner are blocked by the accumulation of dirt and debris, the evaporator coil freezes because of the insufficient airflow to transfer the cold. The pressure drops in the refrigerant, and it causes the switch to turn off low pressure (<50 PSI) and results in interruption of power from the compressor. Therefore, it is imperative to change clean filters.

In addition to cleaning the filters, you must look over and examine the condenser coil to see if there is any accumulation on the outside of the unit. It acts as an insulator in order to eliminate the heat that is absorbed by the space. Therefore, the refrigerant’s pressure is higher and the switch for high-pressure (>450 PSI) of the unit is activated to shut off energy supply for the compressor.

3. Lack of Lubrication:

Sometimes oil contamination (oil leakage, failure of the oil pump or trapped oil inside the suction line) can cause compressor’s malfunction. Be aware that insufficient oil lubricant , or excessive oil levels in the compressor could be the primary causes for this issue. You must check the level of oil in the compressor to resolve the issue.

4. Electrical Problems:

In the majority of cases the unit receives power and the fan in the condenser runs but the compressor isn’t turned on. Voltage or current fluctuations can result in overheating and eventually failure. This leads to frequently breaking off of circuit breakers, which could cause damage to the entire unit. To prevent this, you need engage an HVAC expert to deal with and fix the issue in a perfect manner.

5. Refrigerant Flood back:

The quantity of refrigerant played an important role in the efficiency of the compressor since it must not be either too low or high. If the machine detects a incorrect amount of refrigerant it triggers high- or low-pressure switches which means that the compressor is shut off immediately.

The refrigerant liquid returns to the compressor’s cylinder but not fully vaporizing inside the evaporator as a result of incorrect settings, leakage, or refrigerant overcharge. It damages the compressor due to running pressure. Contact the technician to determine the levels of pressure of refrigerant, and then determine the exact amount needed to ensure that the unit is running correctly.

6. Dead Compressors:

If the compressor is damaged totally, then you need to replace the compressor or the whole unit. If the replacement price lower than half of what the new unit’s price, then you can go for it, or you could opt to buy the new unit.

What to do When the Compressor Won’t Turn On? and How Do I Fix it?

A broken HVAC compressor can leave you get stuck through the summer heat or summer, or in the freezing of winter. Because it is made up of a variety of components, the issue could be caused by any of them fails. Check them thoroughly for the source of the issue and repair or replace the part instead of replacing the whole HVAC equipment or compressor.

Here is some troubleshooting to check and pinpoint the source of the problem, yet remember that most of these can be done by professionals/technicians.

1. Check Electrical Wiring and Power Supply –

In the beginning, make sure the unit is receiving adequate power supply in the event that the heat pump or compressor isn’t turning on. It could be because of the breaker that has been tripped (or) blowing a fuse. But, repeated abrupt stops and starts cause destruction to the compressor, and ultimately the entire HVAC unit. Make sure to check the voltage with the multimeter and examine the entire wiring of the unit, including those that connect directly to outlets.

2. Capacitors –

The capacitors aid in starting and run the compressor blower motor, as well as the outer fan by providing the necessary power. Sometimes, however, it is not able to turn on the compressor because of malfunctioning or damaged capacitors. It can result in an eerie sound emanating from the system as an indication. Replacement of the capacitor and testing the operating condition of the unit is the sole solution to this problem.

3. Start Relays –

As part of maintenance and cleaning tasks technicians must check and replace the starter relay and the capacitor. The starter relay relays the power source through the capacitor into the compressor. It is necessary to shut off the unit when you notice strange sounds because the compressor has gained access to the capacitor that is not working. Remove the old start relay and put in an additional start relay in order to allow the compressor to perform as it should.

4. Terminal Connections –

It is crucial to determine whether the connections on the terminal are secure and tight. We all know that loose connections cause numerous issues, such as problems with the compressor. Also, ensure that the connections are checked and make sure they are set correctly.

5. Valves –

The issue arises because of an inoperative valve. Because refrigerant exists in an liquid substance within the compressor’s intake, when the valves are damaged and the compressor is running, but the unit isn’t working efficiently. All you have to do is check and replace the damaged valves in order to fix this problem.

6. Regular Maintenance –

Maintenance and repair routines (if needed) will not only minimize the possibility of an unreliable compressor, but also prolongs the longevity of the unit. It is imperative to remove the buildup of dirt and debris from the evaporators, filters, and condenser coil could result in overheating the compressor, as well as closing the whole unit. The compressor is extremely efficient and must deal with normal wear and tear, it can be made more difficult when the unit isn’t maintained correctly.

7. Thermostat Settings –

The thermostat itself can be a cause in some instances because it doesn’t signal the unit to turn on the cooling or heating. The unit won’t be able to cool because it incorrectly detects the indoor temperature. This is because of the fact it was set incorrectly or was not installed correctly. The compressor will not start. To fix this, you’ll need examine the batteries and then change them (or) examine the device settings.

8. Winding Problems in the Motor –

The issues with windings within the motor could cause problems for the compressor , since the majority of AC units are equipped with separate compressor motors that are sealed to ensure they are durable to last. If this is the case, you should check the coils of wires within the motor and then replace it when needed. If the compressor’s motor isn’t sealed , then you must compare the replacement or repair cost, and make a smart choice. In addition to the problems with winding caused by power surges, you need examine the thermal switch which shuts off the motor when it is overheated.

9. Lock or Stuck of the Compressor –

A compressor typically requires more power to begin operating, so it draws more power in order to function. In this instance, certain compressors on the model are stopped, turned off or locked up (or) it generates an incessant flow of electricity which causes overheating and, consequently, locking up the compressor. To solve this issue you must hire an expert to repair it and make it function effectively.

HVAC Compressor – Not Turn On FAQs

1. What is the cost to repair the AC compressor?

Answer: The compressor is the most crucial component of the AC system and replacement can be quite costly, since it is dependent on a variety of factors like tonnage (ton – capacity of cooling) the type of compressor of compressor, features that are available and also the brand.
The cost of an AC compressor can range from $2000 to $5000 (excluding the installation costs). The majority of people would rather replace the entire system instead of replacing the compressor after it fails. This is usually the case when the compressor is five or more years old to avoid costs of repair or energy or to make it impossible to repair the problem.2. How to Prevent Breakdowns in the Future?

Answer: We all know that regular HVAC maintenance can make the unit run effectively and smoothly. Additionally, it increases the longevity of the compressor.
But, tackling compressor issues can be quite difficult for people who don’t have any experience. In the majority of cases it is necessary to contact an HVAC expert to identify the problem and get it to run once more. The wear and tear of regular use is the primary cause that can cause the failure of the compressor.
Here are the basics procedures (regular maintenance and timely repairs) that will help you resolve this issue.
* Be sure to conduct the cleaning of your filters as well as condenser coils. supply vents on a regular basis to avoid clogging or blockages that could cause further damage to the compressor.
* It is vital to arrange regular maintenance, with the assistance of technicians in order to maintain exact refrigerant levels, inspect leaks as well as clean out the coil of condenser.
* A minimal wear and tear does not just help keep your unit stay safe, but it can also lower your power costs.
* Replace the entire unit in the event that the compressor of the unit is subject to frequent repairs, this is because repairs will cost greater (in regards to professional hiring and power charges) as compared to the expense of purchasing a brand new unit.
* Check regularly the electrical wiring to determine if there is a circuit breaker that has tripped or a damaged fuse.
* The checklist of the various things like operating pressure/temperature, voltage, proper suction superheat, oil level, and contact points.
* When you hear an audible hum from your equipment it is important to examine for and repair the capacitors, starter relays or switches.
* The majority of these complicated repairs involve hazardous chemical leaks as well as security hazards that need to be handled by specially skilled experts.
* Because HVAC units are utilized to serve seasonal needs. Make sure to inspect the HVAC unit both times both before and after usage.


In conclusion There are many causes that prevent you from turning on your HVAC compressor. We’ve listed some of them. We suggest that hiring an HVAC technician or a professional to thoroughly examine the compressor and all its components and parts.

Repair or replace the component that is being examined instead of replacing the compressor. If the compressor is damaged or has died, then replace the compressor instead of the whole unit. This can save time, effort and cash.

You are welcome to submit your thoughts or questions in the comments section. We’ll help you get those issues resolved.

The article Are You Suffering from an HVAC Compressor not turning on? Here’s How You Fix it appeared first at Electronics Hub.

Michal Pukala
Electronics and Telecommunications engineer with Electro-energetics Master degree graduation. Lightning designer experienced engineer. Currently working in IT industry.