AC Unit Compressor Troubleshooting: Common Issues and Solutions

A faulty compressor can be a major headache, but troubleshooting doesn't have to be. One common issue is a compressor that's not turning on, possibly due to a faulty contactor or a blown fuse.

A worn or damaged compressor contactor can prevent the compressor from receiving power. This can be easily checked by looking for signs of wear or damage on the contactor.

If the compressor is running but not cooling properly, it may be due to low refrigerant levels or a clogged air filter. In this case, a simple refrigerant recharge or air filter replacement can fix the issue.

A compressor that's making unusual noises, such as grinding or screeching, could be a sign of worn or loose internal components.

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Before calling a technician, check for tripped breakers in your service panel. If the breaker looks tripped, turn it off and then back on.

Test the thermostat to ensure it's set correctly and has fresh batteries. Inadvertent changes to the settings could stop the AC from running.

Listen for buzzing or clicking sounds when the system tries to start. If you hear buzzing, the start capacitor may need to be replaced, while clicking sounds can indicate a bad start relay.

Here are some common issues that can cause the compressor to malfunction:

First, turn off the air conditioner at the breaker or fuse box. This is a crucial step to ensure your safety while troubleshooting.

To prevent any accidental starts, make sure to switch off the compressor and unplug the unit. This will also give you a chance to inspect the wires and compressor lugs without any risk.

Now, let's take a closer look at the compressor. Check the wires that lead to the compressor together and take an ohm's reading between Common and Start, Common and Run, and Start to Run.

Here are the typical readings you should expect:

If the readings are outside of these ranges, you may have a problem with the compressor windings.

Remember, an open start winding or run winding can be a sign of a faulty compressor, so be sure to check for any signs of overheating or damage before calling it quits.

Check for blown fuses or tripped breakers before calling a technician. This could be a simple fix that gets your system up and running again.

A faulty or broken capacitor can cause your compressor to malfunction. However, it's unlikely you'll be able to diagnose this issue on your own.

If you suspect an open winding in the motor, disconnect power and remove the top of the outdoor condensing unit. Then, unplug the 3-prong plug on the compressor.

To check for an open winding, set your multi meter to ohms and measure the resistance of each winding. If any of these readings read infinite or over range, you have an open winding.

If you find all the ohm measurements are correct, set your ohm meter to its highest range and measure each pin to the ground. Any measurement that does not read infinite indicates a grounded winding.

Here's a quick rundown of the three motor winding failures:

If you suspect an open winding, be sure to check if the compressor is overheated. If it is hot to the touch, it could be the internal overload has tripped due to overheating.

A locked rotor is a common issue that can happen at the beginning of the season, when the compressor hasn't been running for a while. This can be diagnosed by putting an amp clamp on the Common wire while it's trying to start, which will show the amps skyrocketing beyond its LRA.

The compressor may be stuck, and a hard start kit can sometimes provide the extra kick it needs to get going. However, if the compressor is on borrowed time, it's essential to understand that a new compressor may be needed soon.

Internal overload is another possible cause, where the compressor overheats and shuts down. This can be checked by measuring the resistance between the Common and Start winding, and between the Common and Run windings.

A bad capacitor or hard start kit can cause the compressor windings to overheat or not start at all. It's crucial to check the capacitors and wiring for damage or corrosion, and to have a competent service tech conduct a full evaluation.

Here are some common reasons why AC compressors stop working:

Your AC compressor can stop working due to a variety of reasons. One common cause is a faulty capacitor, which can prevent the compressor from receiving the necessary power to start the cooling cycle.

A locked rotor can also occur, especially at the beginning of the season, when the compressor hasn't been running for a while. This can cause the compressor to try and run, but not pump anything.

Electrical issues, such as tripped breakers or blown fuses, can also prevent the compressor from working. In fact, a blown fuse can be a simple fix, but it's essential to identify the underlying cause to prevent future problems.

Dirty condenser coils, blocked suction lines, and low refrigerant levels can also cause the compressor to stop working. And, if the refrigerant lines are contaminated, it can lead to a situation where the compressor shorts directly to ground.

In addition to these causes, other issues such as burnt wiring, incorrect sizing, and kinks in the lineset can also prevent the compressor from working properly. It's essential to identify and address these issues to prevent future problems.

Here are some common symptoms that may indicate a problem with your AC compressor:

Regular air conditioner maintenance is key to catching and fixing these problems before they become major issues.

Bad Valves? Are You Sure?

Something I hear technicians say a lot is the compressor has a bad valve, but that's not always the case.

Today's scroll compressors don't have valves, they have bearings that can go bad.

If you have decent refrigerant levels but have problems starting and running efficiently with a lot of vibration, or a metal clanking noise, you could have damaged bearings on the compressor.

Refrigerant can wear out the oil, creating a situation where copper plating occurs, which causes the compressor to overheat and draw higher amps.

You'll see higher amp draws on a compressor the hotter it gets outside, but if a compressor is running near its RLA and the refrigerant charge is good, that compressor is hurting.

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A faulty capacitor can cause the compressor to malfunction, leading to a range of issues.

A capacitor failure can result in a blown fuse or tripped circuit breaker, shutting down the AC unit.

Inadequate refrigerant can also cause the compressor to overheat, reducing its lifespan.

A low refrigerant level can be caused by a leak in the system, which can be difficult to detect.

A faulty thermostat can cause the compressor to run continuously, leading to increased energy bills and reduced air conditioning performance.

In some cases, a faulty thermostat can also cause the compressor to overheat, resulting in premature failure.

Here's an interesting read: How to Check Thermostat on Ac Unit

If your AC compressor is on and off cycling frequently, it's likely due to an electrical problem within the compressor.

This is often referred to as a "hard start" and can be a sign of a more serious issue.

Reduced cooling in your home or office can be a symptom of a compressor problem. This can be caused by suction issues that prevent the compressor from working properly.

Overheating is another serious symptom that requires immediate attention. If you notice ice or extreme heat, it's best to call a professional for a proper diagnosis and repair.

Some common symptoms of a malfunctioning AC compressor include frequent on and off cycling, reduced cooling, and overheating.

Regular maintenance is key to preventing AC compressor failures. Our experts can perform compressor inspections and tune-ups to ensure proper operation.

Spotting small issues before they become costly AC emergencies is a major benefit of routine maintenance. You can lower the possibility of failures by regularly changing the air filters and having a certified expert examine the system.

Cleaning the compressor coils is essential, as dirt and debris can build up over time and reduce transmission efficiency. Removing dirt and debris from the outdoor coils improves the compressor's efficiency.

A clogged filter can cause your compressor to work harder and endure more wear and tear. Regularly changing your air filters can help prevent this.

Replacing aging compressors before they fail is another benefit of routine maintenance. This can save you from costly AC emergencies and ensure your system runs efficiently.

Here are some benefits of routine AC compressor maintenance:

Our team takes pride in our work and backs it with excellent service guarantees for our customers. These guarantees include a one-year guarantee on HVAC repairs, prompt service for every visit, cleanliness on the job, and complete customer satisfaction.

Your AC unit compressor is acting up? Before calling a technician, check for tripped breakers, which can often reset the control board and get your system running.

A good rule of thumb is to weigh the cost of repairs against the cost of a new system. If your system is over 10 years old, it's likely nearing the end of its lifespan, which can make replacement a wiser investment. The warranty status of your system is also a consideration, as a near-expired warranty might make replacement more cost-effective.

If you do decide to replace your AC compressor, make sure to hire a skilled expert who can ensure the new piece is compatible with the rest of your system.

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Your air conditioner's compressor is on the fritz, and you're wondering whether to repair or replace it. The decision depends on several factors, including the age of your system.

Most AC compressors last between 10 and 15 years with proper maintenance. So, if your system is still relatively young, repair might be a viable option.

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However, if your system's warranty is near expiration, it might be more cost-effective to replace it. Newer systems are also more energy-efficient, which can lead to significant savings on your utility bills.

A cost-benefit analysis is also crucial. If repairs are becoming frequent and costly, it might be wiser to replace the unit altogether. Here are some key considerations to keep in mind:

If your air conditioner or AC compressor stops running, there are a few simple things you can check before calling a technician.

First, check the breaker for the AC in your service panel. If it looks tripped, turn it all the way off, then back on. This can often reset the control board and get your system running if the problem is minor.

Make sure the thermostat is set correctly and has fresh batteries. Inadvertent changes to the settings could stop the air conditioner from running.

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If the AC compressor starts buzzing and the system doesn’t turn on, the start capacitor may need to be replaced. This should be done by a professional, as it stores high, potentially hazardous voltages.

If you hear a repeated clicking when the compressor engages, and it fails to start, the start relay may be bad. Have it replaced by an HVAC technician.

Here are some common issues to look out for and what to do about them: