How to Use AC Vacuum Pump for Pulling Out the Moisture?

AC vacuum pulling is necessary to ensure no air and moisture remains in the refrigerant system. This is especially helpful before testing, repairs, and recharging the air conditioner. A professional repair performs the vacuum pulling efficiently; however, it never hurts to go the DIY way for how to use ac vacuum pump if you want to.

How To Use Ac Vacuum Pump: Do the Vacuum Pulling In Steps

Before proceeding further with the steps, it is necessary that you have some experience with handling your car. Otherwise, you end up ruining the AC system of your car. Let’s imagine that you the ins and outs of your car, here are the steps to follow-

Prepare the Vacuum Pump

To get with the process of how to use ac vacuum pump, you need to prepare the vacuum first. Get the pump and use the vacuum oil. You can easily locate the vacuum oil cap on the top of the pump and look for the cap-like sign. Unscrew the cap and fill it with oil until it reaches the recommended level.

Tip: always prefer good quality vacuum oil instead of any other oils.

Unscrew the cap
You can easily locate the vacuum oil cap on the top of the pump and look for the cap-like sign (Photo Source: townlec)

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Work the Gauges and Ports

The gauge set enables you to make a connection between the vacuum and pressure ports of the AC system. In the set, the blue gauge needs to connect to the low-pressure service port.

The red gauge will go to the high-pressure port, and the yellow one would go with the gauges to your vacuum. Check all the connections properly as there should not be any loose connections.

Starting the Vacuum Function

Once all the connections are secured, it is time to switch on the vacuum. Every vacuum device has a switch on it, and by flipping the same, get the machine in function. When you see that indicator light or hear the sound, it means that the vacuum is on and ready to work.

In case of any confusion, you should always check the manual that comes along. Get to the side gauge valve and open it; do the same with each side. This makes the device perform the pulling action that sucks the air and moisture from the AC system.

red gauge
In the set, the blue gauge needs to connect to the low-pressure service port (Photo Source: itstillruns)

Continue the Vacuum Operation

The entire process of drawing out moisture and air takes from 15 to 30 minutes. Keep operating the device at full speed and check the manufacturer’s recommendations too. This would let you know how many minutes your AC and vacuum pump should be used to clean the HVAC.

Completing the Process and Closing it Down

Once the vacuum has run for a fine time, you can put the low-side valve to off. You can switch off the valve that connects to the low-side gauge and let the pump hold the vacuum for 15 minutes.

Sometimes, you notice that the hold does not stay for 15 minutes; it means that the components of the pump may likely have a leak. If this is the case, you should consider replacing the parts.

When you have operated using the vacuum for the recommended time, it is time to shut off the pump by using the same switch you used to switch it on. When the vacuum is disengaged, disconnect the AC vacuum and take of all the connecting hoses.

This should make the AC system fully evacuated, or no air and moisture should remain in there. Now, the AC is ready for further operation, such as repair or replacement.

What Would Happen If You Don’t Vacuum the AC System?

An AC system needs refrigerant to circulate the cool air in the cabin. From time to time, you need to refill this refrigerant. Before filling, we go through the AC vacuum process, so all the air or moisture can be drawn out.

The reason drawing out the air is important is because the presence of any of these content directly affects the quality of the AC system. The present moisture would affect the AC’s performance, and the situation can get worse too, in terms of passing the cool air. Explore more about AC and its Maintenance Tips here.

With vacuum, you also take away every day’s dirt and dust that gets accumulated in the AC over time.


We think you are now clear about why it is important to vacuum the AC and how to use ac vacuum pump. Here you need to remember to use the right kind of oil and a quality AC vacuum that does not blow away. In case of doubt, take your car to the professional repair shop and get it done hassle-free.