General air conditioner question

Tiny
NICKL
  • MEMBER
  • 80,000 MILES
I used a vacuum pump to pump down system, left pump running for for a total of forty five minutes. Then closed system overnight. Vacuum held, my question is, does the system reduce moisture while it is closed under vacuum, or does the pump need to be running to reduce moisture?
Friday, July 15th, 2016 AT 6:20 AM

9 Replies

Tiny
NICKL
  • MEMBER
  • 38 POSTS
If your answer is, needs continuous vacuum to reduce moisture, am I accomplishing anything with many fifteen minute pump intervals, or do I need a better pump? Duty cycle on cheap harbor freight pump is ten to fifteen minutes. Thanks for the help.
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Friday, July 15th, 2016 AT 7:31 AM
Tiny
HMAC300
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If it pumped down to about 28 " vacuum and was done for fifteen to thirty minutes then it should be okay, fill the system. When vacuum is applied to the system the vacuum will evaporate the moisture most of the time. If it held then fill the system and do not worry about it.
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Friday, July 15th, 2016 AT 9:40 AM
Tiny
NICKL
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Yes, reached 28". So moisture is removed while vacuum is applied. I flushed the system, So I am trying to make sure all moisture is removed. Does leaving the system closed under vacuum help reduce moisture? Does repeated vacuum of at fifteen minutes do any good in removing moisture?
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Friday, July 15th, 2016 AT 10:18 AM
Tiny
HMAC300
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Once system is closed to pump moisture if any left has no where to go so it has no effect. Repeated vacuuming is normally only good when a Freon sweep is done by that after fifteen minutes Freon is entered into system to try to absorb more moisture then evacuated again. But that is normally only done for a system that has been open to air for years.
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Friday, July 15th, 2016 AT 12:02 PM
Tiny
NICKL
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  • 38 POSTS
Okay thanks. I guess it is as good as its going to get.
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Friday, July 15th, 2016 AT 12:43 PM
Tiny
NICKL
  • MEMBER
  • 38 POSTS
Hi, Still having problems, so I moved the information to 1988 Oldsmobile Cutlass "air conditioner temperature problems. Please take a look, posted more information. Thanks for the help.
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Monday, July 18th, 2016 AT 1:24 PM
Tiny
MHPAUTOS
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Receiver dryer may be saturated, consider replacing this a swell.
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Saturday, July 23rd, 2016 AT 2:25 AM
Tiny
NICKL
  • MEMBER
  • 38 POSTS
Rec dryer is new along with compressor and orifice tube. Yesterday it was 93 degrees and best I could get was 60 degrees at vent. Please take a look at 1988 oldsmobile cutlass ac post. Tried a lot of things, but still looking for improvements. Thanks
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Saturday, July 23rd, 2016 AT 5:33 AM
Tiny
MHPAUTOS
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  • 31,937 POSTS
OK will watch that post now.
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Saturday, July 23rd, 2016 AT 6:53 PM

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