How to Use a Vacuum Pump

How to Use a Vacuum Pump

Table of Contents


When it comes to air conditioning repairs, pulling a vacuum is pretty common. With vacuum pumps, you can easily pull out air as well as moisture from the refrigerant system before repairs, testing, etc.

Besides a vacuum pump itself, you will also need a low-pressure gauge, a high-pressure gauge, and connecting hoses.

I Vacuum pump setting up

Step 1 - Fill your pump with vacuum oil

Prior to using a vacuum pump, you need to fill it with a special vacuum pump oil. Note that other oils may damage your equipment. On the top of the pump, there is an oil fill cap. Unscrew it and you will see the fill line marked on the inner edge. Oil should not cross that line. Fill the opening with oil and replace the oil fill cup.

Fill your pump with vacuum oil

Step 2 - Attach the gauges to the ports

A gauge set is needed to connect to the vacuum pump and the pressure ports on the AC system. Connect the blue gauge and hose to the low-pressure service port. Then, connect the red gauge and hose to the high-pressure port. The yellow hose in the middle should connect the gauges to the vacuum pump. Avoid loose seals. The gauges as well as gauge hoses should be tightly connected.

Attach the gauges to the ports

Step 3 - Open the manifold valves

Use the valves on the AC system that open and close the service port to the refrigerant lines.

Open the manifold valves

II Pulling the vacuum

Step 1 - Start the pump

Turn on your pump using the switch device. You will hear the vacuum running. If it’s cold, open the intake ports until the pump reaches normal running speed. After that, close it off again.

Start the pump

Step 2 - Open the side gauge valve

On the side of each gauge, there are gauge valves. Open them so your vacuum starts pulling air out of the system. Bear in mind that in case you are not sure how to turn the valves to open them, you can always read the manufacturer’s instruction.

Open the side gauge valve

Step 3 - Run your vacuum pump for 15-30 minutes

The vacuum pump should run at full operating speed. It is necessary to pull the air out of the AC system. The exact amount of time for it should be indicated in the user’s guides that come with the vacuum pump and AC system.

Run your vacuum pump

III Vacuum closing

Step 1 - Close the low-side valve & let the vacuum hold for 15 minutes

After letting the vacuum run for some period of time, you need to close the valve that connects to the low-side gauge. Let the pump hold the vacuum for approximately 15 minutes. In case your pump fails to do so for so long, chances are that there is a leak.

Close the low-side valve

Step 2 - Shut off your vacuum pump

Use the same switch mechanism for turning the unit on to turn it off. Prior to disconnecting the system, let the vacuum disengage completely.

Shut off your vacuum pump

Step 3 - Disconnect the vacuum pump

After your vacuum is fully disengaged, disconnect the hose that leads to the pump. Note that at this point, your AC system should be fully evacuated and ready to be recharged/repaired.

Disconnect the vacuum pump

Final thoughts

We hope that now using a vacuum pump is not a problem for you. Just follow the above-mentioned instructions. On our website, choose from a broad range of pumps.

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