How to make a vacuum for cleaning an air conditioning system

It is important to vacuum an air conditioning system to remove any air or moisture that could eventually damage the system. Moisture in the air conditioning system is a serious problem, as moisture reduces the performance of the air conditioning system and water condensation that can cause the air conditioning system to freeze. Condensed water particles corrode the air conditioning system and cause long-term damage. Creating a vacuum deep enough to evaporate moisture using a vacuum pump on a regular basis is a low-cost method of keeping an air conditioning system healthy. Pumps can be purchased or rented, if you don’t want to make a permanent investment.

Turn off the car’s air conditioning and turn off the engine.

Connect the set of pressure gauges for refrigeration. The pump hose should be attached to the low pressure port of the refrigeration gauge. The hose is attached, in simple terms, to the port found in the middle of the gauges. This step is very important in the vacuum of the air conditioning system. This helps maintain a vacuum even after the pump is off. Refrigerant can only be added after the correct level of vacuum is maintained.

Screw the air conditioning vacuum pump to the center valve of the refrigeration gauge set. Keep track of the pressure gauge until the vacuum level reaches 27 Hg. Let the pump run for no less than 30 minutes.

Close the valve that goes to the pressure gauge. Turn the pump to the off position. Leave the equipment in place, without running the pump, for another 30 minutes. After that dead time, check to see if the vacuum level remains at 27 Hg. If the level is less than 27 Hg, then there is a leak in the system that needs to be repaired before proceeding to the next step.

Disconnect the pump hose from the pump and place it in a can of refrigerant or freon after the proper level of vacuum is present and there are no leaks detected. Start the car. Now, turn on the air conditioning system. Open the low pressure manifold slowly to allow the refrigerant, usually Freon, to flow into the system.


Invest in a good electric pump. Keep the pump oiled regularly. Maintain the pump according to the instructions in the manual, and it will probably give you excellent service for 10 years or more. Change the oil in the pump if the pump is running slowly or the oil seems dirty or cloudy.


Using a pressure gauge for refrigeration saves time and money. If the air conditioning vacuum pump is hooked directly into the system, the system will keep losing vacuum each time the connector hose is disconnected from the pump, and the moisture will not effectively evaporate.


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