trying to recharge the a/c system

frosty23_45

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Ok, so I tackled replacing the heater and evap core in my mom's 2005 Jeep Liberty. Was not fun in the slightest. Anyway, so after replacing said parts. Hooked up a can of refrigerant with a gauge on it, showed nothing. Good so far right? So I add a little, compressor still doesn't kick on, go a little more till I hit about 35psi. Compressor kicks on, good. Then it shuts off after about 5 seconds and back on after about 5 seconds and continues to do this. Watching the gauge its going from about 35psi without the compressor running to virtually no pressure when it kicks on, which causes it to shut off. So I'm thinking it's still low, add a little more and then it still does the same thing just more pressure while the compressor is not running and basically nothing when it kicks on.

I know if there's too little pressure the compressor won't kick on, same thing if the pressure gets too high, but wtf am I dealing with here? I let some of the pressure out of the system cause it would go into the red area on the gauge if I turned off the a/c or the car. I'm at the end of my knowledge with the a/c system. Any ideas?
 

bikrboy128

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how big is the can of refrigerant? the system holds ~1.5lbs of freon.

the system needs to be evacuated and put in a vacuum to purge the air and remove all moisture, then charged with the proper amount of refrigerant.

the can of freon is meant for topping the system off, which still isnt the right way to do it but it works.
 

OffshoreDrilling

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It's refrigerant, not freon. That irks me to no end when people say it! freon is DuPont's trade name for R-12 refrigerant.

Like it was said, the system needs to be evacuated with a vacuum pump to remove any air and moisture in the system. The reason you have a high pressure like that is the result of non-condensibles in your system. Refrigeration is a process that involves absorbing and transferring heat by evaporating and condensing refrigerant. Refrigerants have a very specific temperature/pressure relationship as to when they evaporate and condense. All components of a refrigeration system take this into account and are engineered to work specifically with an individual refrigerant. The air and moisture in a system, from not evacuating, do not condense into a liquid in that environment and cause your high pressure situation. Any refrigerant in the system at this point, is also unusable.
 

frosty23_45

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Ok, thanks. Thought I might need to get a vacuum pulled on it. Was gonna see if this would work though. I had 2 - 12 ounce cans btw.
 

Ti28

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how big is the can of refrigerant? the system holds ~1.5lbs of freon.

the system needs to be evacuated and put in a vacuum to purge the air and remove all moisture, then charged with the proper amount of refrigerant.

the can of freon is meant for topping the system off, which still isnt the right way to do it but it works.
Correct! And charging from a vacuum it should be charged as a liquid and not a gas.
 

bikrboy128

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Most shops charge under $100 to evacuate, pull vacuum, and recharge the system. Well worth it imo, the system will never perform right otherwise
 

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