How to Vacuum An AC System Without A Pump

Jessica Stone
by Jessica Stone
You must regularly vacuum your AC system once per year to remove excess moisture, even if you don’t have a pump. Luckily, you can vacuum your AC without a pump if you install access valves on the low and high pressure ends. Let’s take a look at the factors that determine how you can vacuum your AC without a pump and see why it is worth the time and trouble.

There are many ways to improve the overall efficiency of your air conditioning system and reduce the risk of it completely failing. Vacuuming out your AC system is one of these regular maintenance tasks that should never be overlooked. But how do you vacuum an AC system without a pump?

To vacuum an AC system without a pump install an access valve on both ends of the air conditioner system. Depress the access valve on the high side while the pressure on the low side drops as low as it can. Then, you’ll need to charge the low side to 14psi and allow the pressure on both sides to equalize before repeating the process.

It’s essential that you vacuum your system in order to remove any moisture or air that could potentially damage it in the long run. Moisture in the lines is a major issue that reduces the AC system’s performance and can cause freezing.

Eliminating air or moisture in the system on a regular basis is a low-cost, effective way to maintain a healthy air conditioning unit. If you’re installing a new compressor, since most vacuum pumps are driven by the AC grid power, you can run into some difficulty that requires you to implement a different process for evacuation.

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Step One – Depress the Access Valve

With your new compressor and both the high and low side access valves installed, turn on the compressor. Next, depress only the access valve that is located on the high side of the AC system. While you’re doing this, closely observe the pressure on the low side.

One the pressure has reached the lowest point it will reach, close the high-side access valve and shut off the compressor. This entire step will take you around five minutes to complete.

Step Two – Charge the Low Side

After you’ve run through the entire process in step 1, charge the low side of the system. It should be charged completely to roughly 14 psi. Afterwards, wait and monitor for about three minutes until the pressures on both the high and low side equalize.

Step Three – Depress the High-Side Access Valve Again

Once the high and low side pressures level out, turn the compressor back on and depress the access valve on the high side of the system again. Once the pressure on the low side is as low as it will go, allow the high side access valve to close. When closed, turn off the compressor.

Step Four – Repeat Steps 2 and 3.

Once again, charge the low side of the system to around 14 psi. Wait approximately three minutes for the pressure to equalize, turn on the compressor and depress the high-side valve.

Note: A successful evacuation will be indicated by the pressure on the low side not reaching as low as previous. This is due to the refrigerant absorption in the compressor oil and its gradual release.

This time around, when the gas isn’t coming out of the high side access valve, allow the valve to shut. At this point, any air and moisture will have been purged from the AC system.

Step Five – Charge With Refrigerant

For the final step in this evacuation procedure, charge the AC system with the required amount of refrigerant and then shut off the compressor. If necessary, make any appropriate adjustments or changes to this process based on your particular unit.

Why Vacuum an AC System?

As previously mentioned, air and moisture buildup in your AC system can cause a number of problems, some more serious than others. Let’s examine some of the most relevant issues when moisture or air is present in refrigerant and why your system should be vacuumed regularly.

When air exists in refrigerant or refrigerant coils, this can lead to…

  • Reduction in condenser capacity. Air is considered a non-condensate gas and occupies more space than refrigerant in a system. The presence of a non-condensate gas in the system will cause the cooling and condenser capacity to decrease.
  • Less refrigerant charge. With air taking up some of the space that should be occupied by refrigerant, this causes less refrigerant to charge in both the refrigerant system and refrigerant pipe.
  • Increased condenser temperature and pressure. Since non-condensate gases are occupying space, the system does not condense as easily. This leads to an overall increase in pressure and temperature throughout the system.
  • Overheated compressor. As the temperature and pressure of the condenser rises, it enters the evaporate and causes the compressor to overheat. An overheated compressor can lead to higher power consumption and cause the entire compressor system to malfunction or fail.
  • Decrease in cooling capabilities. A compressor that is overheated, increased the power load and energy required to function properly. With more power consumption, the entire system will not be able to cool properly and reduces the overall cooling capacity.

When moisture exists in refrigerant or refrigerant coils, this can lead to…

  • Acid formation. As moisture combines with lubricant in the system, it converts to acid. This chemical reaction causes motor winding failure and rust formation in the system’s internal mechanisms.
  • Expansion Device Blockage. When refrigerant, along with moisture, enter the expansion valve, the moisture blocks the entrance or exit. This blockage of the expansion device can result in ice forming, causing overall freezing and potential failure of the entire system.

How to Vacuum the AC System in Your Car

In order to recharge the air conditioner in your car you have two options. The first option consists of introducing a small amount of refrigerant to recharge the system, while the other option involves vacuuming down and recharging it from scratch. However, this second option does require the use of a vacuum pump, and for the purposes of this article, will not be covered.

When you don’t vacuum the dust and moisture inside of your AC system, the unit can decline in terms of performance. Instead of waiting for a problem to occur, you should perform a cleaning periodically.

In fact, most manufacturers recommend that you have the system vacuumed down every time a service is performed. This helps to remove residual moisture, resulting in a longer lifespan for the compressor.

Simple Recharge with Refrigerant

Follow these steps to perform a simple recharge of your vehicle’s AC system using refrigerant.

  • Safety precautions. Before you begin, park the vehicle on a level surface with the engine off. Apply the emergency break with the transmission in park and make sure that you wear protective eyewear and gloves.
  • Obtain a simple recharge kit. These can be found at your local automotive retailer.
  • Remove the safety, located at the valve base, before getting started.
  • Locate the low side system service port fitted on the larger of the two refrigerant lines. These locations will vary and may be obscured.
  • Once located, remove the low side service port dust cap.
  • While pulling the retainer ring upwards, press the valve over the service port. Note, that the low side fitting will not fit over the high side port. This helps avoid confusion.
  • After attaching the recharge kit, the gauge will indicate the state of charge for the system’s low side pressure.
  • With the kit secure, start the engine and turn the air conditioner on to the highest setting, including the fan speed.
  • After waiting for 30 seconds, the compressor operation will begin. This will be followed by the pressure dropping.
  • Press the plunger valve inward to release the refrigerant into the system. Then, release. The gauge will go up, signaling the transfer from the can into the system. The gauge will drop again once the plunger is released.
  • Continue this process of pressing and releasing until the system has correct pressure. This will be indicated on the gauge. Do not overfill.
  • As the pressure rises, monitor the temperature of the outgoing line of the evaporator and the air vents in the passenger compartment. Both should be cold to the touch.
  • Turn the ignition off. This should shut down the AC and the engine.
  • Pull up on the retainer on the simple recharge kit to release the unit and close the service port.
  • Reinstall the dust cap for the service port.

Congratulations! Your vehicle’s AC system has been successfully recharged using refrigerant.

Relevant Questions

Does vacuuming your AC system remove oil?

You may be wondering if evacuating your system will cause the PAG oil to need to be replaced. Vacuuming out your system will not remove oil. Unless you’ve switched out your accumulator or compressor, you shouldn’t have to replenish the oil.

Do you have to vacuum an air conditioning system in a car?

In order to prevent any of the problems associated with air or moisture in your AC lines, you should also consider evacuating the system in your car in addition to your home.

Additionally, you should always vacuum air or moisture from a car’s air conditioning system prior to filling it up with refrigerant.

What happens if you overcharge your AC?

Overcharging, or having too much refrigerant inside your air conditioner can cause damage to the compressor. The additional refrigerant will collect in the compressor and lead to temperatures that are below normal. It can also flood the compressor and cause destruction to the mechanical components.

Some of the most common symptoms to look out for in the case of too much refrigerant are high discharge temperatures, normal superheats, a high compression ratio and elevated pressures and subcooling in the condenser.

How often should you vacuum your air conditioning system?

In general, experts say that you should perform maintenance on your AC unit once a year. This includes vacuuming out the lines to evacuate any moisture or air that could potentially cause harm.

Spring is typically the best time of year to service your air conditioning system. While most maintenance can be done by yourself, if you notice any major problems, consult a licensed professional.

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Wrapping It Up

It’s very important that you are engaging in annual maintenance on your air conditioning system in order to maintain efficiency. The various tasks include, but are not limited to, replacing filters, cleaning coils and vacuuming the lines.

The most common method for evacuating your AC system is by using a vacuum pump, but this is not the only course of action. By following the steps outlined above, you can successfully conserve efficiency, performance and prevent any damage caused by the existence of air or moisture in both your home’s and your vehicle’s AC system.

For more questions related to your HVAC system, check out “ How Long Should It Take a House To Cool from 80 To 72 Degrees?” and “ Why Won’t My Heat Pump Go Into Defrost Mode?

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Jessica Stone
Jessica Stone

Jessica considers herself a home improvement and design enthusiast. She grew up surrounded by constant home improvement projects and owes most of what she knows to helping her dad renovate her childhood home. Being a Los Angeles resident, Jessica spends a lot of her time looking for her next DIY project and sharing her love for home design.

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