Quote:
Originally Posted by MarKoBrow
Perhaps you might want to check your pressures before recharging, it sounds more like you have a expansion valve that is getting clogged
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This is a very good possibility if R-134a was added to a system that had mineral oil in as a lubricant.
You can leak check a very small system with a standing vacuum test. You should let it stand for 24 hours blanked off from the pump. A big leak will show up fast, a very small leak won't.
If you have removed the refrigerant to do a repair and need to do a leak check (good idea) there will probably be enough refrigerant left in the system and in the oil to work as a trace gas when the system is pressurized with dry nitrogen. Then you can use an electronic leak detector that is capable of finding very small leaks.
You could do a standing pressure test, but changes in ambient temperature may give you the impression that the pressure has changed.
If there is a question as to what refrigerant you have in the system, if there is enough refrigerant in the system to exist as both liquid and vapour, you can check the saturation chart to determine what refrigerant you have in the system. If you have a blend of refrigerants installed (ex R12 replacement gas and R12) you will not be able to determine what gas is in the system this way.
A vacuum gauge is a valuable tool when evacuating a system. You can test the ability of the pump to pull a good vacuum. (some can't) and the vacuum level inside the system. Even if you have the smallest of leaks, you will not be able to reach below 1000 microns. A good vacuum is 500 microns, acceptable is 750 on an system with residual oil/refrigerant.
Don't forget to do regular oil changes on the vacuum pump. Old oil with moisture in it will reduce the ability of the pump to pull low.