How to Use a Vacuum Pump

PDF download Download Article
Everything you need to know about your vacuum pump, from setting it up to shutting it down
PDF download Download Article

Pulling a vacuum is a common part of air conditioning repairs. Vacuums are used to evacuate ACs, a process by which they pull out all air and moisture from the refrigerant system prior to testing, repairs, and recharging. Generally, this is best done by an HVAC professional. If you are looking to do simple at-home repairs, though, learning to use a vacuum pump could be very helpful.

How to Use an A/C Vacuum Pump

  1. Fill your pump with vacuum oil.
  2. Connect your gauges to the ports and open the manifold valves.
  3. Start the pump and open the side gauge valve.
  4. Let the vacuum run for 15–30 minutes total.
  5. Shut down the low-side valve and give the vacuum 15 minutes to hold.
  6. Shut off the vacuum pump.
  7. Disconnect the hosing to the pump.
Part 1
Part 1 of 3:

Setting up Your Vacuum Pump

PDF download Download Article
  1. Before you use your vacuum pump, make sure it is full of clean vacuum pump oil. Unscrew the oil fill cap, typically located on the top of the pump, and look on the interior edge of the opening for the fill line. Fill the opening with oil until it reaches that line. Then, replace the oil fill cap. [1]
    • Be sure to only use oil meant for vacuum pumps. Using other mechanical oils could impact the quality and performance of your vacuum.
  2. You will need a gauge set that connects to both your vacuum and your pressure ports on your AC system. The blue gauge and hose should connect to the low-pressure service port. The red gauge and hose will connect to the high-pressure port. The yellow hose in the middle should connect your gauges to your vacuum. [2]
    • Make sure the gauges and gauge hoses are connected tightly. Loose seals can compromise your vacuum.
    • In your car, your high-pressure port will generally be physically higher than the low-pressure port. [3]
    Advertisement
  3. Once you have your gauges in place, you will need to use the valves on your AC system that opens and closes the service port to the refrigerant lines. With the valves closed, your gauges should have little to no pressure reading. [4]
    4. Advertisement
Part 2
Part 2 of 3:

Pulling the Vacuum

PDF download Download Article
  1. After you are sure everything has been securely connected, use the switch device on your vacuum pump to turn it on. You should be able to hear the vacuum running once it is switched on. [5]
    • If you are trying to start the pump in cold weather, open the intake ports until the pump reaches normal running speed. Then, close it off again. [6]
  2. Once your vacuum is on, you will need to open the gauge valves, located on the side of each gauge. This allows the vacuum to start pulling air out of the system. [7]
    • If you are unsure which way you need to turn your valves to open them, check the manual that came with your gauges or vacuum.
  3. Let your vacuum run at full operating speed for at least 15 minutes and up to 30 to completely pull the air out of your AC system. The exact amount of time you will need to let your vacuum run will vary based on your manufacturer’s recommendations, so check any operational manuals you may have for both your AC system and vacuum pump. [8]
    • Generally, you want to let your vacuum run for at least long enough to get the measurement below 1,000 microns. If you can, try to get it down to 500 microns.
    4. Advertisement
Part 3
Part 3 of 3:

Closing Your Vacuum

PDF download Download Article
  1. After you have let your vacuum run for a sufficient amount of time, close the valve that connects to the low-side gauge. Let your pump hold the vacuum for 15 minutes. [9]
    • If it’s not able to hold for that long, you likely have a leak and may need to replace components on your vacuum pump.
  2. When you are satisfied with how long your system held the vacuum, shut the pump off using the same switch mechanism you used to turn it on. Let your vacuum disengage completely before you disconnect the system. [10]
  3. Once your vacuum has fully disengaged, you can disconnect the hose leading to the pump. Your AC system should be fully evacuated at this point, and ready to be recharged or repaired. [11]
    • If you have a drain issue, one of the most common problems in air conditioning, you can get a Co2 drain gun and an AC drain brush to clean the clog in the drainage system. It is better than using chemicals. [12]
    • You should also replace filters regularly. It will help prevent clogs and debris collection on the bottom of the condensate drain pan.
    • You can even get condensate pan tablets to prevent drain clogs.
    4. Advertisement

Community Q&A

Search
Add New Question
  • Question
    What do you use to collect the freon when vacuuming the system?
    Yvette Melgoza
    Community Answer
    When vacuuming a system, a refrigerant recovery machine is typically used to collect and store the freon. This specialized equipment ensures the safe retrieval and containment of the refrigerant, adhering to environmental regulations while preventing the freon's release into the atmosphere.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
    Yes No
    Not Helpful 6 Helpful 6
  • Question
    What type of vacuum pump is suitable for a reverse cycle split air conditioner?
    Yvette Melgoza
    Community Answer
    A rotary vane vacuum pump is commonly used. It's efficient in removing air and moisture from the system, ensuring proper functioning during both heating and cooling cycles. Its design suits the needs of HVAC systems, making it a suitable choice for reverse cycle split air conditioners.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
    Yes No
    Not Helpful 5 Helpful 0
Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit
      Advertisement

      Video

      Tips

      Submit a Tip
      All tip submissions are carefully reviewed before being published
      Name
      Please provide your name and last initial
      Submit
      Thanks for submitting a tip for review!

      Things You'll Need

      • Vacuum pump
      • Low-pressure gauge
      • High-pressure gauge
      • Connecting hoses

      You Might Also Like

      How to
      Replace the Batteries in Most Models of Honeywell Thermostat
      How to
      Install a Split System Air Conditioner
      How to
      Clean Split Air Conditioners
      How to
      Measure Airflow
      How to
      Install a Portable Air Conditioner
      How to
      Clean & Maintain a Window Air Conditioner
      3 Easy Ways to Reset an Air Conditioning Unit That’s Not Working
      How to
      Install a Condensate Pump
      How to
      Clean the Filter on Your Air Conditioner
      How to
      Put Freon in an AC Unit
      How to
      Clean an Evaporator Coil
      How to
      Replace an Air Conditioning Unit's Run Capacitor
      How to
      Install an Inwall Air Conditioner
      How to
      Charge a Home Air Conditioner
      Advertisement

      References

      1. ↑ http://yellowjacketuniversity.com/articles/the-evacuation-and-charge-process/
      2. ↑ https://www.carid.com/articles/how-to-use-an-air-conditioning-manifold-gauge-set.html
      3. ↑ https://www.2carpros.com/articles/re-charge-an-air-conditioner-system
      4. ↑ https://www.2carpros.com/articles/re-charge-an-air-conditioner-system
      5. ↑ https://www.2carpros.com/articles/re-charge-an-air-conditioner-system
      6. ↑ http://yellowjacketuniversity.com/articles/the-evacuation-and-charge-process/
      7. ↑ https://www.2carpros.com/articles/re-charge-an-air-conditioner-system
      8. ↑ http://www.denlorstools.com/autoblog/2012/05/car-ac-vacuum-pumps-faqs/
      9. ↑ https://www.2carpros.com/articles/re-charge-an-air-conditioner-system
      1. ↑ http://yellowjacketuniversity.com/articles/the-evacuation-and-charge-process/
      2. ↑ https://www.airconditioning-systems.com/air-conditioning-vacuum-pump.html
      3. ↑ https://iso-tip.com/how-does-a-co2-drain-gun-work

      About This Article

      Article Summary X

      To use a vacuum pump on an air conditioner, first, turn the pump on and open the side gauge valve, which will allow the vacuum to start pulling air out of your system. Once the valve is open, let your vacuum run at full speed for 15 to 30 minutes to pull out as much air as it can. The exact amount of time you need to let the pump run will depend on the manufacturer, so check the operational manual for a specific time. After the vacuum has run long enough, close the valve that connects to the low-side gauge and let your pump hold the vacuum for 15 minutes. Then, shut off the pump and disconnect the hose leading into it. For more tips, including how to know if your pump has a leak, read on.

      Did this summary help you?
      In other languages
      Thanks to all authors for creating a page that has been read 381,350 times.

      Reader Success Stories

      • Sam Merani

        May 25, 2020

        "This is most accurate site to learn from. I am a new technician just learning. Thank you."
      Share your story

      Did this article help you?

      Advertisement