How to Choose a Vacuum Pump for your Automotive Shop
July 1, 2006
A vacuum pump has several uses for the auto air conditioning mechanic and automotive shop. The main purpose of a vacuum pump is to remove air and moisture from your automobile air conditioning system. Moisture is a serious threat to your car’s air conditioning system. Moisture will move through the refrigerant line as fine mist and crystallize wherever it expands. Also, when moisture mixes with refrigerants it will become extremely corrosive. You won’t notice this damage until it’s too late. A vacuum pump removes moisture by creating a vacuum in the air conditioning system. The low pressure will boil off the moisture at very low temperatures. This will vaporize the water and vent it out through the system. Now the next issue is what is the best type and size of vacuum pump to use. First, there are 2 types you will come across. The cheapest is a venturi type vacuum pump that runs from your shop air compressor. Venturi pumps are popular with the home mechanic crowd since they are cheap and easy to use. However, they are limited by the fact that they it is very hard to boil off much moisture with one of these types of vacuum pumps. They just will not pull a good a vacuum as you need. The best and most common vacuum pumps that are found in a professional auto shop is a good electric vacuum pump. Every professional air conditioner mechanic and auto shop have at least one. You now have to decide what make and model to purchase or rent. Most vacuum pumps have a CFM rating on the box. This indicates how much air volume the pump can remove from the system. The more air the pump can move, the quicker it will achieve the proper vacuum. There is also two stage and single stage pumps. Also, the two stage pumps are quicker and more efficient, but a single stage will get the job done. If you are using a vacuum pump on a passenger car up to 10 tons, a 1.2 cfm pump will work fine. If you are working on a air conditioning system in a large truck or RV, you will probably need to move up to a 4 cfm model. Now that you have chosen the proper vacuum pump for your automotive shop, you will need to properly maintain this piece of equipment. The main thing is to change the vacuum pump oil frequently. You should immediately change the oil if: 1. You have just evacuated an air conditioning system that was contaminated with moisture. 2. The air conditioner had a compressor burnout and evacuated the system. 3. The vacuum pump oil looks “cloudy” or “milky”/. 4. Your vacuum pump will not pull the factory rated micron range.
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