General AC question

Using a vacuum pump to leak test the low pressure side of the AC plumbing, making sure that it holds the vacuum "indefinately", which to me would mean 24 to 48 hours, could you also leak test the high
pressure side AC plumbing the same way, or would the vacuum have some adverse affect on the expansion valve or other components?
Or does putting the vacuum on the low pressure side open the expansion valve to extend the vacuum to the high side?
Thanks sleepdog
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You're supposed to vacuum the entire system. There is no high/low side consideration when evacuating the air from the system. You need to remove all of the air to prevent it from reacting with the refrigerant. In addition, air contains moisture, which will ruin the dessicant in the system. When you hook the pump up you should ideally rotate the compressor by hand a few turns to ensure all of the air is able to escape. You run the vacuum pump through the R-12/R134 gauges from the same port you would normally apply a refrigerant charge. After pulling the system down for an hour or so close both valves on the gauges and check to see that the system does not lose vacuum. If all is well hook up a can and charge 'er back up.
I wouldn't waste time trying to do this job with a handheld pump. Rent an electric one and do it right.
Chris
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Yep, that's what I'm planning. I just didn't want to create a big problem with a little information. The system in question has no charge since it all leaked out way back. So while I have the top end tore down I'm going to replace the accumulator, expansion valve and put some new seals in where I can. Will also flush and replace the oil prior to. Should be fun.
Thanks!
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