It is important to vacuum an air-conditioning system to remove any air or moisture that may damage the system in the long run. Moisture in the AC system is a serious problem, because moisture reduces the performance of the AC system and condensation of water can cause the AC system to freeze. Condensed water particles corrode the AC system and cause long-term damage. Creating a vacuum deep enough to boil moisture away by using a vacuum pump on a regular basis is an effective, low-cost method of maintaining a healthy AC system. Pumps can be purchased or rented, if you don’t want to make a permanent investment.
Turn off the air conditioning in the car and switch off the car engine. Hook up the refrigerant gauge manifold set. The pump hose should be attached to the low-pressure port of the refrigerant gauge. The hose is attached, in simplified terms, to the port that is found in the middle of the gauges. This step is very important in vacuuming the AC system. It helps maintain the vacuum even after the pump shuts down. Refrigerant can be added only after the correct level of vacuum is maintained.