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#1
07-11-2009, 11:00 AM
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Not evacuating system
What would be the end result if you did not evacuate the a/c system before refilling it after it was all apart? Thanks
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1974 Grand Prix Model J |
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#2
07-11-2009, 12:16 PM
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It wouldn't work. First of all, getting enuf R-whatever into the system to allow the pressure switches to get the compressor to run is problematic. Secondly the moisture in the air in the system could freeze up inside, not allowing the refridgerant to flow, IIRC.
Getting the air and stuff out allows just refridgerant and oil to be in the system..that's what it's designed for. George
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"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
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#3
07-11-2009, 12:22 PM
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Short answer? It's NOT an option to not evacuate a refrigerant system into a deep vacuum (less than 500 microns) before charging. Your system will not work if the air and moisture are not removed before charging with refrigerant. Longer answer? Air is a non-condensable, meaning that it will not be condensed in the condenser, but rather, it will take up space and cause your system pressures to be too high to properly absorb and reject heat. Moisture in the air will also cause a lot of problems as it reacts with the refrigerant and oil.
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John  "There are no stupid questions, but there are a LOT of inquisitive idiots!" |
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#4
07-11-2009, 01:10 PM
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Well an idiot I guess told me that I didnt have to. We put the freon in and it did work idling to about 64F then eventually was 100F. That could possibly be the cause. We have installed new Expansion valve, lines, POA vlave and a condensor. Replaced all O-rings. All the lines were cold that were supposed to be then were very hot. Long story short-It has an appointment at a shop Monday morning. Leave it to the pros. Do you think it was freezing up due to all the air and moisture?? Thanks
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1974 Grand Prix Model J |
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#5
07-11-2009, 02:28 PM
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Yes. Don't evacuate it to get it all out, how will you even know if it holds vacuum? It could have leaked all right out in 5 minutes.
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#6
07-11-2009, 03:03 PM
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Make sure you tell the guys at the shop that it's full of air before you let them hook their recovery equipment to it! When you asked this question I wish you had said that you had already done this and was planning on running the system. I would have told you not to start it! As you witnessed, air gets hot when it's compressed! I hope you didn't damage the compressor, because the pressures were probably through the roof!
They will have to blow the charge and not recover it as the air in your system could possibly damage their recovery unit. Once the system is pulled down into a vacuum, they should break the vacuum with nitrogen and pressurize the system to leak check it. You should also change the drier, as it was exposed to moisture laden air. Once they are sure that the system is tight they will pull it down into a deep vacuum again and weigh in the system charge.
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John "There are no stupid questions, but there are a LOT of inquisitive idiots!" |
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#7
07-11-2009, 03:14 PM
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Quote:
Once the repair is made the system is "topped off". I still don't like this method as you can't be sure how much refrigerant remained before you topped off. I like to start with an empty, evacuated system and weigh in the nameplate charge on critically charged systems. Critically charged means a system that doesn't have TXV (thermostatic expansion valve), but rather a fixed orifice or capillary tube. These systems require the "exact" amount of charge listed on the nameplate. TXV systems can be charged using the sub cooling method. This meaning that you add refrigerant until you get the correct condensed liquid line temperature for the given refrigerant.
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John "There are no stupid questions, but there are a LOT of inquisitive idiots!" |
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#8
07-11-2009, 04:30 PM
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John,
Seems you are very knowlegeable about this. Thanks for the info and I will make sure they know what we have done.
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1974 Grand Prix Model J |
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#9
07-16-2009, 11:52 AM
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fwiw.....i have a 97 jeep 4.0 & the compressor bearing went bad on me. i bought a used replacement & hooked it back up without charging it. then, over a year later decided to buy a couple bottles of r134 & put them in without evacuating the system....it works great! blows ice coold & has worked for 2 years now with no problems at all.....
guess i was lucky 
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