Pulling Vacuum On AC System (Its Purpose, How-To, Cost)

why pull a vacuum on ac system

The air conditioning system of your car is a fragile component that often needs to be cleaned and checked to ensure that it is in optimal working condition.  Air and moisture are your biggest enemy and these can build up significantly if you don’t pull a vacuum on the AC system.

What Happens If You Don’t Pull A Vacuum On An AC System?

You should ideally vacuum the AC system to help remove any moisture buildup. Leaving it could cause long-term damage and cause the AC to freeze over. Additionally, it increases the condenser pressure and temperature. The battery might drain more rapidly. The last thing is the damaged AC compressor.

By running the vacuum over the component, you will be removing some of the moisture and air, while reducing the pressure.

Any pressure or moisture should boil away with the ambient temperatures created by the vacuum, which completely cleans the unit and makes it functional. Now, you can add your refrigerant to ensure your AC works and keeps the car cool when activated.

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What Is The Purpose Of Pulling A Vacuum On An AC System?

1. Restore Refrigerant Charge

You want to remove excess air. While air might not seem relevant, it does occupy space inside the AC. If you have too much air, you could reduce the refrigerant charge of your AC system.

Let’s say that air occupies 30% of the space, you will only have 70% of refrigerant and this means that only 70% of refrigerant will charge.

2. Increased Condenser Pressure And Temperature

Air is a non-condensable gas and when it occupies too much space inside your AC, you notice that the refrigerant does not condense as effectively. Since the main goal of the AC is to reduce the temperature, having less condenser pressure and condensation will reduce the efficacy of the AC unit.

3. Reduce Power Consumption

One thing you want to avoid is consuming more power with your vehicle. Since everything is tied to the battery, it could lead to long-term performance loss. If your AC does not effectively do everything it should, it will work harder to try and do this. Unfortunately, this could lead to less cooling and more power consumption.

4. Failing Compressor

The final thing you want to avoid is having a compressor that fails or gets damaged. It is best to have the AC in optimal condition, as having the compressor be overworked, means that it could be damaged and you will have to replace it. The vacuum process removes all of these possibilities and ensures all the capacity is put towards cooling.

How To Pull A Vacuum On An AC System?

1. Setting Up The Vacuum

The first important step is making sure the vacuum pump is full of clean vacuum pump oil. To do this, you would want to unscrew the oil fill cap and look at the fill line to ensure adequate oil is inside and that it reaches the fuel line.

Next, you would want to attach the gauges for the vacuum and pressure ports on your AC system. Generally, you have a red and blue gauge and the red gauge connects to the high-pressure port. The blue gauge connects to the low-pressure port, while the yellow hose connects your gauges to the vacuum.

Finally, you have to check the manifold valves. When they are closed, the gauges should have no pressure. However, when they are open, the pressure on the gauges will start rising significantly.

2. Pulling The Vacuum

The next step would be starting the vacuum process and this entails turning on the vacuum pump. The vacuum should make a noise to indicate that it is actively working. After the vacuum is working, you want to open the side gauge valves that enable the vacuum to use the suction. The suction will allow the vacuum to start pulling air from the system.

It should run for about 30 minutes, but some people choose to only vacuum the AC for 15-minutes. I have found that 30-minutes is ideal to allow the vacuum to pull out most of the air. Keep in mind that there are various vacuum brands and all of these will have to run for different periods to fully pull out all the air.

Ideally, you want to have a measurement of under 1,000 microns to ensure that you have enough air removed. If you have a better vacuum, you might want to aim for getting it beneath the 500-micron level.

3. Finishing Up

Once you are satisfied that enough has been removed from the AC, you can close the low-side valve, while letting the vacuum hold for about 15-minutes. If the vacuum does not hold as long, you might be dealing with a leak.

If everything is fine and your vacuum is holding, you can turn off the vacuum. It is important to let the vacuum disengage completely before removing it from the AC. If the vacuum is fully disengaged, you can remove the vacuum from the AC and disconnect the components.

How Much Does It Cost To Pull A Vacuum On AC System?

The costs should be in the range of $200. However, certain situations spike the costs closer to $300. The additional costs are often labor-related and checking all the systems can be labor-intensive. Many people often have to dole out an additional $150 for the labor cost.

The great thing about vacuuming your AC is that you can do it at home when you have the vacuum. Unfortunately, these tools can be very expensive.

How Long Does It Take To Draw A Vacuum On AC System?

If you do the vacuum process often, you won’t have as many gases or air moisture built up inside and this will reduce the time needed for drawing the vacuum on your AC system. In essence, it should not take more than 1-hour. However, the vacuum process can take about 30-minutes.

If any leaks are discovered, the mechanics will need to spend additional time finding the leaks. Since AC is an intricate component in many cars, finding minor leaks and issues can be a tiresome job.

If you have your own vacuum and you want to do it at home, it could take much longer. You should consider spending time with the instructions to know what your vacuum is capable of doing. Once you understand the power of the vacuum cleaner, it becomes much easier to determine how long the process should take.

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