Quote:
Originally Posted by LarryBible
In my experience, I have found very few a/c pro's who are even aware of the measurement of vacuum in terms of microns. If you have a vacuum meter that will give you microns, it would be very good to see 100 microns.
If the truth could be known, I fully expect that most a/c systems rarely get evacuated much below 1,000 microns. If for no other reason than the fact that many people don't change the oil in their vacuum pumps often enough.
I have given lots of thought to coughing up the money for such a vacuum meter, but other needs keep cropping up diverting the funds.
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My pump is rated at 25 microns, but in reality it will get to a solid 100 microns if it is dead-headed into the gauge. Add hoses and things get tricky. Add a car and things get impossible. The pressure goes slowly down, pops up a few hundred microns, slowly goes down, etc. Each time the pressure popped up, it popped up to a lower maximum than before, so it was working. Four hours later and the spikes were all below 400.
I don't recall the chart, but 1000 will get the job done in warm weather. It won't be enough if you're doing the job in the winter.