Identifying and resolving issues with an air conditioning compressor can be a daunting task. However, with a few simple steps, you can easily test your AC compressor and determine if it needs repair or replacement. This guide will provide you with a comprehensive walkthrough of the testing process, ensuring that your AC system operates at peak efficiency and keeps you comfortable during the hot summer months.
Prior to initiating the testing procedures, it is crucial to ensure that safety precautions are strictly adhered to. Always disconnect the power supply to the AC unit before commencing any electrical work. Wear appropriate safety gear, including gloves and safety glasses, to protect yourself from potential hazards. Once safety measures are in place, you can proceed to gather the necessary tools and materials required for testing, such as a multimeter, a thermometer, and a pressure gauge.
The initial step involves checking the electrical supply to the compressor. Utilize a multimeter to measure the voltage and amperage at the compressor terminals. Compare the obtained readings with the manufacturer’s specifications to determine if the compressor is receiving adequate power. Proceed to inspect the capacitor connected to the compressor; a faulty capacitor can prevent the compressor from starting. You can test the capacitor using a multimeter’s capacitance setting. If the capacitor is defective, it should be replaced. Next, examine the compressor contactor; a faulty contactor may impede the compressor from receiving power. You can test the contactor using a multimeter’s continuity setting.
Visual Inspection
A visual inspection of your AC compressor is a quick and easy way to identify potential issues. Here are some things to look for:
1. **Physical damage:** Check the compressor for any dents, cracks, or leaks. These could indicate that the compressor has been damaged and may need to be replaced.
| Physical Damage | Impact |
|---|---|
| Dents | Compromised compressor housing integrity, leading to potential leaks or internal damage. |
| Cracks | Severe structural damage, allowing refrigerant leakage and compromising system functionality. |
| Leaks | Loss of refrigerant, leading to decreased cooling efficiency and potential system failure. |
2. **Oil leaks:** Oil leaks can be a sign that the compressor’s seals are damaged. This can lead to a loss of lubrication, which can cause the compressor to overheat and fail.
3. **Electrical connections:** Check the electrical connections to the compressor. Make sure they are tight and free of corrosion. Loose or corroded connections can cause the compressor to malfunction.
4. **Refrigerant leaks:** Refrigerant leaks can be detected by using a refrigerant leak detector. A refrigerant leak can cause the compressor to overheat and fail.
Electrical Tests
Electrical tests assess the electrical integrity of the AC compressor and its components.
1. Continuity Test
Using a multimeter, check for continuity between the following pairs of terminals:
- Run terminal and common terminal
- Start terminal and run terminal
- Start terminal and common terminal
If any of these pairs show an open circuit, the compressor may have a faulty winding or connection.
2. Resistance Measurement
Measure the resistance between the following terminals:
| Terminals | Resistance |
|---|---|
| Run and Common | 0.5 – 5 ohms |
| Start and Run | 10 – 50 ohms |
| Start and Common | 15 – 60 ohms |
Deviations from these ranges can indicate a winding problem or a short circuit.
3. Voltage Test
With the compressor running, measure the voltage across the following terminals:
- Run terminal and common terminal
- Start terminal and run terminal
- Start terminal and common terminal
The voltage readings should be within the manufacturer’s specifications. Deviations can point to problems with the power supply, capacitor, or compressor windings.
Pressure Tests
1. Static Pressure Test
The static pressure test verifies that the compressor can hold pressure without leaking. To perform this test, follow these steps:
- Connect a pressure gauge to the low-pressure side of the compressor.
- Close the service valves on both the high and low-pressure sides of the compressor.
- Use a vacuum pump to evacuate the system to a vacuum of at least 29 inches of mercury.
- Close the vacuum pump and observe the pressure gauge. The pressure should hold for at least 15 minutes without dropping by more than 2 inches of mercury.
2. Running Pressure Test
The running pressure test verifies that the compressor can maintain adequate pressure while operating. To perform this test, follow these steps:
- Connect a pressure gauge to both the high and low-pressure sides of the compressor.
- Open the service valves on both sides of the compressor.
- Start the compressor and run it for at least 15 minutes.
- The high-pressure gauge should read between 100 and 150 pounds per square inch (psi), and the low-pressure gauge should read between 5 and 10 psi.
3. Discharge Pressure Test with Amps
The discharge pressure test with amps measures the amperage draw of the compressor while it is running at a specific pressure. This test can help diagnose problems with the compressor’s valves or bearings. To perform this test, follow these steps:
- Connect an ammeter to the compressor’s power supply.
- Connect a pressure gauge to the high-pressure side of the compressor.
- Start the compressor and run it at a specific pressure, typically between 100 and 150 psi.
- Record the amperage draw of the compressor.
- Compare the amperage draw to the manufacturer’s specifications. If the amperage draw is higher than the specified limit, it could indicate a problem with the compressor’s valves or bearings.
| Test | Purpose | Procedure | Results |
|---|---|---|---|
| Static Pressure Test | Verify that the compressor can hold pressure without leaking |
– Connect a pressure gauge to the low-pressure side of the compressor. – Close the service valves on both the high and low-pressure sides of the compressor. – Use a vacuum pump to evacuate the system to a vacuum of at least 29 inches of mercury. – Close the vacuum pump and observe the pressure gauge. |
Pressure should hold for at least 15 minutes without dropping by more than 2 inches of mercury |
| Running Pressure Test | Verify that the compressor can maintain adequate pressure while operating |
– Connect a pressure gauge to both the high and low-pressure sides of the compressor. – Open the service valves on both sides of the compressor. – Start the compressor and run it for at least 15 minutes. |
– High-pressure gauge should read between 100 and 150 psi – Low-pressure gauge should read between 5 and 10 psi |
| Discharge Pressure Test with Amps | Measure the amperage draw of the compressor while it is running at a specific pressure |
– Connect an ammeter to the compressor’s power supply. – Connect a pressure gauge to the high-pressure side of the compressor. – Start the compressor and run it at a specific pressure. – Record the amperage draw of the compressor. |
– Amperage draw should be within the manufacturer’s specifications |
Continuity Tests
Continuity tests are essential for determining if a circuit is complete and functioning properly. These tests involve sending a low-voltage current through a circuit and measuring the resistance to flow. With a continuity tester, you can identify breaks in wires, faulty connections, or open circuits.
To perform a continuity test on an AC compressor, follow these steps:
- Unplug the AC compressor from the power source.
- Set your multimeter to the lowest ohms setting.
- Connect the black probe of your multimeter to the “GND” terminal on the AC compressor.
- Touch the red probe of your multimeter to the following terminals on the AC compressor, one at a time:
| Terminal | Expected Continuity |
|---|---|
| C | Continuity |
| R | Continuity |
| S | Continuity |
| L1 | No Continuity |
| L2 | No Continuity |
If you get continuity readings between the “C”, “R”, and “S” terminals, it indicates that the windings on the AC compressor are intact. If you get no continuity readings, it suggests that there is a break or fault in the windings and the AC compressor may need to be replaced.
If you get continuity readings between any of the “C”, “R”, or “S” terminals and the “L1” or “L2” terminals, it indicates a short circuit and the AC compressor may need to be replaced.
Temperature Monitoring
With a thermocouple or temperature probe, you can measure the temperature of the suction line and discharge line after the unit has been running for about 15 minutes. You can make sure that the compressor is functioning properly and that the refrigerant is flowing effectively by comparing the temperature readings to the manufacturer’s recommendations. The following table offers general temperature ranges for various types of compressors:
| Compressor Type | Suction Line Temperature (℉) | Discharge Line Temperature (℉) |
|---|---|---|
| Reciprocating | 20-40 | 120-160 |
| Scroll | 30-50 | 130-170 |
| Centrifugal | 40-60 | 140-180 |
| Screw | 50-70 | 150-190 |
Note that these ranges are only general guidelines, and the actual temperatures may vary depending on the specific model and operating conditions of the compressor. If the temperatures you measure are significantly different from the recommended ranges, it may indicate an issue with the compressor or refrigerant system and further troubleshooting may be necessary.
Performance Evaluation
To evaluate the performance of the AC compressor, several tests can be conducted. These tests aim to assess the compressor’s efficiency, capacity, and overall functionality.
1. Capacity Test
The capacity test determines the compressor’s ability to cool the desired space effectively. This test involves measuring the amount of cooling produced by the compressor under controlled conditions and comparing it to the manufacturer’s specifications.
2. Efficiency Test
The efficiency test evaluates the compressor’s energy consumption relative to its cooling output. This test measures the compressor’s Energy Efficiency Ratio (EER), which indicates the amount of cooling produced per unit of energy consumed. A higher EER signifies greater efficiency.
3. Noise Test
The noise test assesses the amount of sound produced by the compressor during operation. This test is important for ensuring that the compressor does not create excessive noise that may disturb occupants.
4. Reliability Test
The reliability test evaluates the compressor’s ability to withstand extended periods of operation without failure. This test typically involves running the compressor continuously for a specified duration to identify any potential issues or weaknesses.
5. Leak Test
The leak test checks for any leaks in the compressor’s refrigerant system. This test is essential for ensuring that the compressor maintains proper cooling performance and does not contribute to refrigerant emissions.
The following table summarizes the key tests used to evaluate AC compressor performance:
| Test | Purpose |
|---|---|
| Capacity Test | Assesses cooling ability |
| Efficiency Test | Measures energy consumption relative to cooling output |
| Noise Test | Evaluates sound produced during operation |
| Reliability Test | Assesses ability to withstand extended operation |
| Leak Test | Checks for refrigerant leaks |
Refrigerant Analysis
Refrigerant analysis is a crucial step in testing an AC compressor. This analysis helps determine the refrigerant level, its purity, and whether there are any leaks or leaks within the system. Here are the steps involved in refrigerant analysis:
1. Gauge Manifold Connection:
Connect a gauge manifold to the AC system’s service ports. This manifold has three gauges: low-pressure, high-pressure, and vacuum gauges.
2. Refrigerant Level Check:
With the system running, observe the refrigerant pressure readings on the low-pressure gauge. The pressure should be within the manufacturer’s specifications, indicating the correct refrigerant level.
3. Refrigerant Leak Detection:
Turn off the AC system and close the service valves. Use a refrigerant leak detector to scan for leaks along the piping, joints, and fittings. If a leak is detected, it will produce an audible or visual signal.
4. Vacuum Test:
Connect a vacuum pump to the AC system and evacuate it to remove any air or moisture. The vacuum should hold for at least 30 minutes without any significant pressure rise, indicating a leak-free system.
5. Refrigerant Charging:
If the refrigerant level is low, charge the system with the appropriate refrigerant type and amount as per the manufacturer’s specifications. Use a refrigerant recovery and charging machine for this process.
6. Refrigerant Pressure Monitoring:
Once the refrigerant is charged, monitor the high-pressure and low-pressure gauges. The pressures should stabilize within the normal operating range, indicating proper refrigerant flow.
7. Leak Monitoring over Time:
It’s essential to monitor the refrigerant pressure and temperature readings over time to ensure there are no leaks or refrigerant loss. If the pressure drops significantly or the system becomes inefficient, further investigation should be conducted to identify and repair any issues.
| Measurement Parameter | Normal Operating Range |
|—|—|
| Low-Pressure Gauge | 40-60 psi |
| High-Pressure Gauge | 180-250 psi |
| Vacuum Level | -29 inHg or better |
Checking the Refrigerant Level
Low refrigerant levels can cause the compressor to run constantly and overheat. Use a refrigerant gauge to check the level and add refrigerant if necessary.
Inspecting the Electrical Connections
Loose or damaged electrical connections can prevent the compressor from receiving power. Check all the connections and tighten or replace any that are loose or damaged.
Checking the Capacitor
A faulty capacitor can prevent the compressor from starting. Use a multimeter to test the capacitor’s capacitance and resistance. Replace the capacitor if it is defective.
Troubleshooting Common Issues
Compressor not starting
Check the power supply, electrical connections, capacitor, and refrigerant level.
Compressor running constantly
Check the refrigerant level, condenser coils, and airflow.
Compressor making noise
Check for loose parts, refrigerant leaks, or a faulty compressor.
Compressor overheating
Check the refrigerant level, condenser coils, airflow, and electrical connections.
Compressor tripping the circuit breaker
Check the electrical connections, capacitor, and compressor for shorts or overloads.
Compressor freezing up
Check the refrigerant level, evaporator coil, and airflow.
Compressor not cooling
Check the refrigerant level, condenser coils, evaporator coil, and airflow.
Safety Precautions
Working with electrical systems can be dangerous. It’s important to take the following safety precautions before testing your AC compressor:
1. Disconnect power to the AC unit
Turn off the circuit breaker or remove the fuse that powers the AC unit. This will prevent you from getting shocked while working on the compressor.
2. Wear protective clothing
Wear safety glasses, gloves, and long sleeves when working on the compressor. This will protect you from flying debris and electrical shocks.
3. Use a multimeter to check the voltage
Before touching any electrical components, use a multimeter to check the voltage. This will ensure that the power is off and that it’s safe to work on the compressor.
4. Discharge the capacitor
The capacitor in the compressor can store a large amount of electricity. Before touching any electrical components, discharge the capacitor by touching the two terminals together with a screwdriver.
5. Ground yourself
Ground yourself by touching a metal object that’s connected to the ground. This will prevent you from getting shocked if you accidentally touch a live wire.
6. Be aware of your surroundings
Be aware of your surroundings and make sure that there are no children or pets in the area. Electrical work can be dangerous, so it’s important to be careful and aware of your surroundings.
7. Don’t work on the compressor if you’re not comfortable
If you’re not comfortable working on the compressor, don’t do it. It’s better to call a qualified electrician to do the work for you.
8. Follow the manufacturer’s instructions
If you’re not sure how to test the compressor, refer to the manufacturer’s instructions. This will ensure that you’re testing the compressor correctly and safely.
9. **Additional Safety Tips for Your Specific Compressor**
| Compressor Type | Additional Safety Tips |
|---|---|
| Central Air Conditioner | – Turn off the power to the outdoor unit at the breaker panel. – Disconnect the wires from the compressor terminals. – Test the voltage at the terminals to make sure it’s 0 volts. – Discharge the capacitor by touching the two terminals together with a screwdriver. – Ground yourself by touching a metal object that’s connected to the ground. |
| Window Air Conditioner | – Unplug the air conditioner from the outlet. – Remove the front panel of the air conditioner. – Test the voltage at the compressor terminals to make sure it’s 0 volts. – Discharge the capacitor by touching the two terminals together with a screwdriver. – Ground yourself by touching a metal object that’s connected to the ground. |
| Portable Air Conditioner | – Unplug the air conditioner from the outlet. – Remove the back panel of the air conditioner. – Test the voltage at the compressor terminals to make sure it’s 0 volts. – Discharge the capacitor by touching the two terminals together with a screwdriver. – Ground yourself by touching a metal object that’s connected to the ground. |
Tools You’ll Need
Multimeter
Refrigerant pressure gauge
Thermometer
Safety glasses
How to Test an AC Compressor
1. Safety First
Before you begin, put on safety glasses. Refrigerant can leak from the compressor, so it’s crucial to protect your eyes.
2. Check the Electrical Connection
Use a multimeter to check if the compressor is getting power. Set the multimeter to AC volts and connect the leads to the compressor terminals. You should read a voltage reading that matches the voltage of your home’s electrical system.
3. Test the Compressor Capacitor
The capacitor stores electrical energy to help the compressor start. Use a multimeter to check if the capacitor is working. Set the multimeter to capacitance and connect the leads to the capacitor terminals. You should read a capacitance reading within the manufacturer’s specifications.
4. Check the Compressor Pressure
Connect a refrigerant pressure gauge to the compressor’s service ports. The pressure reading should be within the manufacturer’s specifications. If the pressure is too high or too low, the compressor may not be working properly.
5. Check the Compressor Temperature
Use a thermometer to measure the temperature of the compressor. The temperature should be within the manufacturer’s specifications. If the compressor is too hot or too cold, it may not be working properly.
6. Check for Loose Parts
Inspect the compressor for any loose parts. Loose parts can cause the compressor to fail. If you find any loose parts, tighten them securely.
7. Listen for Unusual Noises
When the compressor is running, listen for any unusual noises. Unusual noises can indicate a problem with the compressor. If you hear any unusual noises, turn off the compressor and call a qualified technician.
8. Check the Refrigerant Level
Use a refrigerant pressure gauge to check the refrigerant level. The refrigerant level should be within the manufacturer’s specifications. If the refrigerant level is too high or too low, the compressor may not be working properly.
9. Check the Condenser Coil
The condenser coil helps to remove heat from the refrigerant. Inspect the condenser coil for any dirt or debris. If the condenser coil is dirty or clogged, it can prevent the compressor from working properly.
10. Check Other Components
If all of the above tests are normal, the compressor may still not be working properly. Other components that can affect the compressor’s operation include the thermostat, the fan motor, and the evaporator coil. If you are unable to diagnose the problem yourself, call a qualified technician.
Recommended Maintenance
| Task | Frequency |
|---|---|
| Clean the condenser coil | Monthly |
| Check the refrigerant level | Annually |
| Have the compressor inspected by a qualified technician | Every 2-3 years |
How to Test AC Compressor
An air conditioning (AC) compressor is a vital component in your home’s cooling system. It compresses refrigerant gas, which helps to remove heat from the air inside your home. If your AC compressor is not working properly, it can lead to a number of problems, including increased energy bills, decreased cooling efficiency, and even a complete system failure.
There are a few different ways to test an AC compressor. One way is to use a multimeter to check the voltage and amperage at the compressor terminals. Another way is to use a pressure gauge to check the pressure of the refrigerant in the system. If the voltage, amperage, or pressure are not within the specified range, it may indicate that the compressor is not working properly and needs to be replaced.
People Also Ask
How do I know if my AC compressor is bad?
There are a few signs that may indicate that your AC compressor is bad. These include:
- The AC unit is not cooling your home properly
- The AC unit is making a loud noise
- The AC unit is leaking refrigerant
- The AC unit is tripping the circuit breaker
Can I test my AC compressor with a multimeter?
Yes, you can test your AC compressor with a multimeter. To do this, you will need to set the multimeter to the AC voltage setting and then touch the probes to the compressor terminals. The voltage should be within the specified range for your compressor.
How do I check the pressure of the refrigerant in my AC system?
To check the pressure of the refrigerant in your AC system, you will need to use a pressure gauge. To do this, you will need to connect the pressure gauge to the refrigerant lines on your AC unit. The pressure should be within the specified range for your refrigerant.
