Complete Guide: How To Change Air Conditioner Compressor

Complete Guide: How To Change Air Conditioner Compressor

Is your car’s air conditioner blowing warm air? Does it make strange noises? You might have a bad AC compressor. Can you change an AC compressor yourself? Yes, you can. It is a big job. It needs special tools. This guide will show you how to do it. It covers every step. This includes how to get out the old refrigerant. It also covers how to put in the new one. This guide will help you fix your car’s AC.

Signs of a Bad AC Compressor

Knowing when your AC compressor is failing is the first step. Look for these common signs. They point to a problem. This helps in troubleshooting AC compressor failure.

Diminished Cooling Performance

• Warm air: The most common sign. Your AC blows warm air. It should blow cold air.
• Weak air flow: Air comes out slowly. It is not strong. This can mean a problem.
• No cold air: The AC simply does not get cold. This is a clear sign.

Unusual Noises from the Engine Bay

• Grinding: A harsh, scraping sound. It often means parts are rubbing.
• Whining: A high-pitched noise. It gets louder with engine speed.
• Clicking: A rapid clicking sound. This happens when you turn on the AC. It means the clutch might be bad.
• Squealing: A loud, high-pitched noise. It can mean a loose belt. It can also mean a seized compressor.

Visible Leaks or Damage

• Greenish fluid: Look for green or yellow fluid. It is often under the compressor. This is refrigerant oil with dye.
• Oily residue: An oily film might be on the compressor. This shows a leak.
• Damaged clutch: The front part of the compressor. It might look worn out. It might be broken.

AC Compressor Clutch Issues

• Not engaging: The clutch should click. It should spin when the AC is on. If it does not, it is bad.
• Stuck engaged: The clutch spins all the time. Even when the AC is off. This is a problem.
• Burning smell: A hot, burning smell. This can come from a slipping clutch.

If you see these signs, your AC compressor might be bad. It might be time for AC compressor replacement.

Why Replace an AC Compressor?

The AC compressor is the heart of your car’s air conditioning system. It moves refrigerant. This gas makes your car cold. When it breaks, your AC stops working.

Replacing a bad compressor brings back cold air. It makes your drive more comfortable. It also helps keep your car’s value. A working AC is important for resale.

Tools and Materials Needed

You need special tools for this job. Make sure you have them all. This makes the DIY AC compressor change easier.

Essential Tools

• Manifold Gauge Set: This tool checks AC pressures. It is a must-have.
• Vacuum Pump: This pump removes air. It removes moisture from the AC system. You need it before adding new refrigerant.
• Refrigerant Recovery Machine: This machine safely takes out old refrigerant. You must not release refrigerant into the air. It harms the environment. Some auto parts stores rent these.
• AC Charging Machine (Optional): This tool adds new refrigerant. It is accurate.
• Wrench Set (Metric and Standard): You will need many sizes.
• Socket Set (Metric and Standard): For bolts and nuts.
• Ratchet: For sockets.
• Pliers (Various Types): For hoses and clamps.
• Screwdrivers (Flat and Phillips): For small parts.
• Serpentine Belt Tool or Breaker Bar: To loosen the belt.
• Torque Wrench: To tighten bolts correctly. This is very important.
• Drain Pan: To catch fluids.
• Funnel: For adding oil.
• Safety Glasses: To protect your eyes.
• Work Gloves: To protect your hands.
• Jack and Jack Stands: To lift the car safely.
• Wheel Chocks: To keep the car from rolling.

Essential Materials and Parts

• New AC Compressor: Make sure it fits your car. Get the right model.
• New Accumulator or Receiver Drier: You must replace AC accumulator. It stores refrigerant. It also filters moisture. This part must always be changed with the compressor.
• New Orifice Tube or Expansion Valve: This part helps cool the refrigerant. It should also be replaced.
• PAG Oil: This is special oil for AC systems. Make sure it is the right type. It needs to match your car’s system. The PAG oil amount is very important.
• New O-Rings and Seals: These tiny rings prevent leaks. They often come with the new compressor.
• Refrigerant (R-134a or R-1234yf): Use the correct type for your car. Check your car’s label.
• Flushing Solvent (Optional but Recommended): To clean the old system. This removes old oil and debris.
• Belt (Optional): If your serpentine belt is old or cracked.
• Blue Shop Towels or Rags: For cleaning spills.

Safety First

Working on your car’s AC system can be dangerous. Refrigerant is under high pressure. It can cause frostbite. It can also harm your eyes. Follow these safety rules.

• Wear Safety Glasses: Always wear them. Protect your eyes from splashes.
• Wear Gloves: Thick work gloves protect your hands.
• Work in a Well-Ventilated Area: Do not breathe in refrigerant vapors. Work outside or in an open garage.
• Do Not Smoke: Refrigerant can react with flames. It creates harmful gas.
• Keep Away from Open Flames: No smoking, no open heaters.
• Never Release Refrigerant into the Air: It hurts the ozone layer. Use a recovery machine.
• Disconnect the Battery: Before you start work, disconnect the negative battery cable. This prevents electric shock. It also prevents the car from starting by accident.
• Use Jack Stands: Never work under a car supported only by a jack. Use sturdy jack stands. Chock the wheels.

Preparing for AC Compressor Replacement

Good prep makes the job easier. It also makes it safer.

Accessing the Compressor

1. Park on a Flat Surface: Make sure the car is level.
2. Set the Parking Brake: Secure the car.
3. Lift the Car: Use a jack. Place jack stands safely.
4. Remove Parts Blocking Access: You might need to take off engine covers. You might need to remove a wheel. You might need to remove a fender liner. Check your car’s repair manual. Each car is different.

Refrigerant Evacuation and Recharge

This is a critical step. You must remove the old refrigerant. This is called refrigerant evacuation.

1. Locate Service Ports: Find the high-side and low-side AC service ports. They usually have caps. They look like tire valve stems. The low-side port is smaller.
2. Connect Manifold Gauge Set:
   • Connect the blue hose to the low-side port.
   • Connect the red hose to the high-side port.
   • Connect the yellow hose to the recovery machine.
3. Start Recovery Machine: Follow the machine’s directions. It will pull the refrigerant out. It stores it safely.
4. Monitor Gauges: Watch the gauges. They should drop to zero. The system is empty when both gauges read zero.
5. Turn Off Recovery Machine: Close the valves on the gauge set. Disconnect the hoses.

Important: If you do not have a recovery machine, you cannot do this step. You must take your car to a shop. They can recover the refrigerant safely. Releasing refrigerant into the air is illegal in many places. It is also bad for the environment.

Removing the Old Compressor

Now you can take out the broken compressor.

1. Loosen Serpentine Belt: The serpentine belt drives the compressor. Use a belt tool or breaker bar. Turn the tensioner pulley. This loosens the belt. Take the belt off the compressor pulley.
2. Disconnect Electrical Connector: Find the wire harness plugged into the compressor. Unplug it carefully.
3. Disconnect AC Lines: There are two AC lines going to the compressor. One is high pressure. One is low pressure.
   • Use a wrench to loosen the nuts or bolts.
   • Be ready for a small puff of gas. Even after recovery, some gas might remain.
   • Move the lines aside.
4. Unbolt the Compressor: The compressor is held by several bolts. They can be tight.
   • Use the correct size socket.
   • Remove all mounting bolts.
   • Make sure nothing else is attached.
5. Remove the Old Compressor: Carefully pull the compressor out. It can be heavy.
   • Place it in a drain pan. Old oil might leak out.

Replacing Associated Components

When you do AC compressor replacement, you must replace other parts. This prevents early failure of the new compressor.

Replace AC Accumulator or Receiver Drier

This is a very important step. You must replace AC accumulator whenever you open the AC system. It removes moisture. It also catches debris.

1. Locate Accumulator/Drier: It is a metal canister. It usually sits in one of the AC lines.
2. Disconnect Lines: Loosen the connections.
3. Remove Old Unit: Take it out.
4. Install New Unit: Put the new accumulator in.
   • Make sure new O-rings are in place.
   • Tighten connections.
   • The new accumulator is open to the air. It quickly absorbs moisture. Install it quickly. Do not leave it open for long.

Replace Orifice Tube or Expansion Valve

This part helps the refrigerant expand and cool. It often clogs when a compressor fails.

1. Locate and Remove:
   • Orifice Tube: It is usually inside one of the AC lines. It looks like a small plastic tube. You might need a special tool to pull it out.
   • Expansion Valve: It is usually at the firewall. It is bolted to the evaporator.
2. Install New Part: Put the new orifice tube or expansion valve in.
   • Use new O-rings.
   • Lubricate O-rings with PAG oil.

Preparing the New AC Compressor Installation

Before putting the new compressor in, do these steps.

Check PAG Oil Amount

Your new compressor might come pre-filled with oil. Or it might be empty. You must check the PAG oil amount. Too much or too little oil is bad.

1. Check Old Compressor Oil:
   • Pour all oil from the old compressor into a measuring cup.
   • Note the amount. This is how much old oil was in it.
2. Check New Compressor Oil:
   • If it has oil, pour it out and measure it.
   • Compare to your car’s total system oil capacity. This is in your car’s manual.
3. Adjust Oil Level:
   • Rule of Thumb: Match the oil amount removed from the old compressor. Add this to the new one.
   • Better Way: Drain all oil from the new compressor. Add the exact amount needed for your car’s entire system. Then subtract the oil that will be in the new accumulator/drier and condenser. This is tricky.
   • Simplest for DIY: Drain the new compressor. Add 2-4 ounces of fresh PAG oil. This assumes you replaced the accumulator/drier. The rest of the oil is already in the system’s other parts (condenser, evaporator).
   • Important: Use the correct type of PAG oil. (e.g., PAG 46, PAG 100, PAG 150). Check your car’s manual.

Table: Common PAG Oil Types by Vehicle Year (General Guide)

Always check your car’s specific manual for the correct PAG oil type and total system capacity.

Lubricate O-Rings

Every connection point needs new O-rings.

• Dip each new O-ring in fresh PAG oil.
• Place them on the lines and fittings. This helps them seal. It prevents leaks.

New AC Compressor Installation

Now put the new compressor in its place.

1. Position New Compressor: Carefully slide the new compressor into place.
2. Install Mounting Bolts: Hand-tighten all bolts first. Do not fully tighten yet.
3. Connect AC Lines:
   • Attach the AC lines to the new compressor.
   • Make sure the new O-rings are in place.
   • Tighten the bolts or nuts. Use a torque wrench. Tighten to car maker’s specs. This is very important to prevent leaks.
4. Connect Electrical Connector: Plug in the wire harness.
5. Reinstall Serpentine Belt: Put the belt back on the pulleys. Make sure it is routed correctly. Use the belt tool to release the tensioner.
6. Tighten Mounting Bolts: Once all lines are connected, tighten the compressor mounting bolts. Use a torque wrench. Tighten to car maker’s specs.

Vacuum Pump AC System (Evacuation)

This step removes air and moisture. Air and moisture are very bad for AC systems. They can cause major damage. This is called vacuum pump AC system.

1. Connect Manifold Gauge Set:
   • Connect the blue hose to the low-side port.
   • Connect the red hose to the high-side port.
   • Connect the yellow hose to the vacuum pump.
   • Make sure all valves on the gauge set are open.
2. Start Vacuum Pump: Turn on the pump.
3. Monitor Gauges: Watch the gauges. They should drop deep into the vacuum side. Aim for at least 29.5 inches of mercury (inHg). Or -100 kPa.
4. Pull Vacuum for 30-60 Minutes: Let the pump run. This pulls out all air and moisture. Longer is better, especially if the system was open for a long time.
5. Close Gauges, Turn Off Pump:
   • First, close the valves on the manifold gauge set.
   • Then, turn off the vacuum pump.
   • Leave the gauges connected.
6. Perform a Vacuum Hold Test: Watch the gauges for 15-30 minutes. The needle should not move. If it rises, you have a leak. You must find and fix the leak. Then repeat the vacuum process. Do not add refrigerant if there is a leak. This is a critical AC system pressure test.

Recharging the System

Once the system holds vacuum, you can add refrigerant. This is part of refrigerant evacuation and recharge.

1. Connect Refrigerant Can:
   • Connect the yellow hose from the gauge set to your refrigerant can’s tap valve.
   • Open the refrigerant can’s valve.
   • Purge the yellow hose: Briefly loosen the yellow hose at the manifold gauge. A small hiss of refrigerant will escape. This removes air from the hose. Then tighten it.
2. Add Refrigerant (Low Side Only):
   • Start the car.
   • Turn the AC to max cold. Set fan to high.
   • Open only the low-side valve (blue) on the manifold gauge set.
   • The compressor should cycle on and off.
   • The refrigerant will be pulled into the system. You might need to gently shake the can.
3. Monitor Pressure: Watch the low-side gauge.
   • Do not overfill. Refer to your car’s manual for the correct refrigerant amount. It is usually in ounces or pounds.
   • Add small amounts. Let the system settle.
   • Stop filling when the low-side pressure is correct. (Usually 30-40 psi with compressor running). The high-side pressure should also be within range. (Often 150-250 psi). These pressures depend on outside temperature.
4. Turn Off Car and AC:
   • Close the low-side valve on the gauge set.
   • Turn off the car.
   • Remove the gauge set.

Testing the System

After charging, test your work. This is the final AC system pressure test.

1. Start Engine: Let it run.
2. Turn on AC: Set to max cold, high fan.
3. Check for Cold Air: Feel the air coming from the vents. It should be cold.
4. Listen for Compressor: The clutch should engage and disengage smoothly.
5. Check for Leaks: Use a leak detector. Or use soapy water on connections. Look for bubbles.
6. Drive the Car: Take it for a short drive. Test the AC under different conditions.

Common Mistakes to Avoid

Avoid these errors for a successful new AC compressor installation.

• Not Replacing Accumulator/Drier: This is the most common mistake. The old drier is full of moisture and debris. A new compressor will fail fast if you do not replace it.
• Not Flushing the System: If the old compressor failed completely (seized, metal bits), you must flush the system. This cleans out debris. Skipping this will damage the new compressor.
• Incorrect PAG Oil Amount: Too much or too little oil is bad. It can cause compressor failure.
• Wrong PAG Oil Type: Using the wrong type of oil can harm the system.
• Not Pulling a Deep Vacuum: Leaving air and moisture in the system leads to poor cooling. It also causes damage.
• Overcharging/Undercharging: Too much or too little refrigerant reduces cooling. It also stresses the compressor. Use the exact amount stated in your car’s manual.
• Not Using New O-Rings: Old O-rings leak. Always use new ones.
• Not Checking for Leaks: A slow leak will empty your system. Always check for leaks.
• Releasing Refrigerant: This is harmful and illegal. Always use a recovery machine.

When to Call a Professional

While DIY AC compressor change is possible, it is a complex job. Consider a pro if:

• You lack the right tools: Especially the recovery machine and vacuum pump.
• You are unsure about any step: Mistakes can be costly.
• You suspect a major system issue: Like a clogged condenser or evaporator.
• You cannot find and fix a leak: Pros have better leak detection tools.
• The system needs flushing: This can be tricky without the right equipment.
• It’s automotive AC repair, not just parts swap: If you need to diagnose other problems.

A professional automotive AC repair shop has the training and equipment. They can do the job safely and correctly.

Maintenance Tips for Your AC System

After all this work, keep your AC running well.

• Run AC Regularly: Even in winter. Run your AC for 10-15 minutes once a month. This keeps seals lubricated. It prevents problems.
• Check Cabin Air Filter: A dirty filter can block airflow. It can make your AC work harder. Change it often.
• Keep Condenser Clean: The condenser looks like a small radiator. It sits in front of your car’s main radiator. Keep it free of leaves and debris. Clean it gently with water.
• Listen for Changes: Pay attention to new noises or smells. Early detection can save money.
• Annual Check-up: Have a professional check your AC system yearly. They can spot small problems before they become big ones.

Conclusion

Changing an AC compressor is a big task. It needs special tools. It needs patience. But with this guide, you can do it. You can save money. You can get your cold air back. Remember safety first. Follow all steps carefully. If you are ever unsure, ask for help. Or call a professional. Enjoy your cool ride!

Frequently Asked Questions (FAQ)

Q1: How long does an AC compressor replacement take?

A1: For a skilled DIY person, it can take 4-8 hours. It depends on your car. It also depends on your experience. A professional shop can do it in 2-4 hours.

Q2: Do I have to replace the accumulator/drier when I change the compressor?

A2: Yes, absolutely. It is crucial. The accumulator absorbs moisture. It collects debris. When you open the AC system, the old one fills with moisture from the air. A new compressor needs a fresh, dry system.

Q3: What happens if I use the wrong PAG oil?

A3: Using the wrong PAG oil can damage the compressor. It can also damage other parts. It might not mix well with the refrigerant. This causes poor lubrication. Always use the specific type and amount listed in your car’s manual.

Q4: Can I skip the vacuum pump AC system step?

A4: No, you should never skip it. Pulling a vacuum removes air and moisture from the system. Air and moisture can mix with refrigerant. This forms acids. These acids eat away at AC components. This causes new parts to fail fast. It also makes your AC cool poorly.

Q5: My AC is still not cold after changing the compressor. What could be wrong?

A5: Many things can cause this.
* Leak: You might have a leak somewhere else. Check all connections.
* Incorrect Refrigerant Charge: It might have too much or too little refrigerant.
* Clogged Orifice Tube/Expansion Valve: If you did not replace it, it could be clogged.
* Clogged Condenser: Debris can block airflow.
* Electrical Issue: A sensor or relay might be bad.
* New Compressor Faulty: Rarely, a new part can be bad.
* You might need a professional to diagnose it.

Carlos Gadd

My name is Carlos Gadd, and I am the creator of AirPurityGuide.com.. With a passion for footwear, I share my experiences, insights, and expertise about shoes. Through my blog, I aim to guide readers in making informed decisions, finding the perfect pair, and enhancing their footwear knowledge. Join me on this journey to explore everything about shoes!