Quote:
Originally Posted by Bob Kontak
Regarding a vacuum, it is never mandatory to pull a vacuum before recharging, but you are not eliminating moisture that has crept into the system. Even the el-cheapo air compressor driven vacuum pump from Harbor Freight is WAY better than nothing.
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I have never before seen anyone say that.
From everything I have ever read or heard a vacuum is very necessary before a recharge if you want the AC system to function.
There will be a lot of moisture in the system, and about 14 psi of pressure of air. Air is not a refrigerant. The moisture will freeze and clog up the expansion valve.
I run my vacuum pump for long time to make sure all the moisture is boiled out. I am a belts and suspender type. I pressurize the system with dry nitrogen after pulling a vacuum and then pull a vacuum again. I want a DRY system.