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A/C System PSI

Discussion in 'Projects, mods, restoration' started by rampage, Jun 10, 2017.

  1. rampage

    rampage Active Member

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    How much pressure does an A/C system operate ?
     
  2. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    There is no one number, not even for a particular car. It's dependent on the refrigerant charge, the ambient temperature, engine speed, type of refrigerant, etc. Ambient temp is the biggest factor. Generally speaking, high-side pressure can be anywhere from 180 to over 300 psi, low side can be 12-40 psi. If you are not familiar with or trained in A/C maintenance, DO NOT attempt to work on a system. You can be injured or killed, and the system can be damaged.
     
  3. rampage

    rampage Active Member

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    That answers it, thank you
     
  4. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    It doesn't really answer it. As I said, pressures vary widely with temperature and fill. Do not attempt any work based on the numbers I posted. You need to know the weight and the pressures designed for your specific vehicle, and how much the pressure changes with temperature.
     
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  5. rampage

    rampage Active Member

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    Car had front end damage. I had to replace the condenser and receiver. Got a can of 134 at Wal-Marts with the gauge on it and filled the system. Seems to be working fine now. Just was curious about that high side pressure.
     
  6. ImperialCrown

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    Was the system vacuumed down before charging the system? If regular air is mixed in with the refrigerant, it won't cool as well, high-side pressures can be way too high and compressor damage can result.
    You haven't said what you are seeing for high-side pressure.
    The PAG oil lost in the discharge and component replacement must be replenished or else the low oil can also damage the compressor.
     
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  7. Doug D

    Doug D Virginia Gentleman

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    I believe those kits are for "topping off" a system, and NOT for refilling a system that has been damaged and repaired or where components have been replaced.

    Just my opinion, but if an A/C system has lost freon, there is more than likely a leak somewhere which would have to be identified and repaired. Then as Imperial noted, a vacuum should be drawn and held steady (Bob would recommend for at least an hour) - any time the system has been opened to the outside environment this needs to be done. Then using a proper gauge set refill the system to the proper levels. To do that you need the proper training - as Bob noted to refill you need to know the weight and pressures for your specific vehicle. This is not one size fits all.

    No, I'm not licensed or trained in A/C work, but I know enough to defer this type of work to someone who is.
     
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  8. rampage

    rampage Active Member

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    I understand your points. The car is a 18 year old $1000 heap and don't want to start pouring money into it for A/C. Could use more important fixes. Got about $75 into this A/C system so far and that's it. If it fails I'll cut the belt. It has been working fine so far,and the next three days are suppose to be 90 degree stinkers so that'll be the test. I plan on giving it to my son when he gets his license back. If it fails he can take it to a shop if he wants A/C. Thanks for your reply. A/C systems are a gray area for me but I'm learning.
     
  9. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    If you spent the money for a condenser and drier, you should have taken the time to evacuate the air out of the system. Air not only reduces the performance of the system, it contains a significant amount of moisture, which will also reduce performance, but more importantly, form acid which eats away at the system from the inside out. So essentially, you wasted $75 and long-term (1 to 3 years, maybe) will destroy the system. I'll bet a mechanic would have charged you as little as $25 extra just to evacuate it. And that would have told you if there was a leak.
    The idea is to learn all about them before doing any work, not learn as you go.
     
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  10. rampage

    rampage Active Member

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    Thank you for your input. I'll look into it.
     

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