Prostar A/C blows hot within 30 mins

Discussion in 'International Forum' started by CMCtech, Aug 7, 2014.

  1. CMCtech

    CMCtech Bobtail Member

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    Feb 20, 2013
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    Several Prostars a/c in my fleet have been blowing cold but after 30mins-1hr they go hot. If we turn the truck off and start it right back up, it blows cold once again. Need help with this headache
     
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  3. RSQ20

    RSQ20 Medium Load Member

    You need to get a set of manifold gauges on the system and check the pressure conditions when the system fails....

    .... Philip
     
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  4. tumblin dice

    tumblin dice Light Load Member

    201
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    Apr 18, 2014
    Jacksonville, FL
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    Could be a faulty low side pressure switch......this cycles the compressor on/off
     
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  5. texasmorrell

    texasmorrell Medium Load Member

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    May 3, 2012
    Lone Star State
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    This is a very common problem and it is easily fixed. Your thermistors have gone bad. They're sending bad signals to your body controller ECM and your ECM is shutting off your compressor. It will reset each time you cycle the key. This is why it works each time you start the truck. But it will only work for 15 minutes until it shuts off the AC compressor. Just buy two thermistors. Then go to a shop and have them evac the system. It only takes two minutes to replace the thermistors then the technician can recharge your system and it will be fixed. This problem is so common on the ProStar it is recommended that you carry extra thermistors with you in the truck. You need to educate yourself on your ProStar AC system. There is an excellent set of seven short videos by Rawze on YouTube about the ProStar air-conditioning system. Just do a search on YouTube for "fix your ProStar AC yourself ". Then you'll know exactly what to do the next time your air-conditioning system stops working. Don't let a repair shop rip you off.
     
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  6. jkgillian

    jkgillian Bobtail Member

    4
    0
    Sep 27, 2009
    Hohenwald, TN
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    Okay so I am stumped. I watched The videos by Rawze and read all that I can find and I still can't quite figure this out. I have a 10 prostar and a/c issues. I burned the comp. clutch up on Friday which put me without cold air. I changed the clutch and it started blowing cold again. I left Saturday morning and it blew for an hour and quit blowing cold. I thought maybe it was low even though the clutch was still engaging so I put in some refrigerant. It blew colder than it ever had before for most of the day, then quit again about 1600 yesterday and nothing I try can make it fire back up. The clutch engages, but blows hot air. I checked both thermistors and the bottom one reads 2500 ohms and the top one 1500(I hope I am saying that right) which should mean they are both good according to Rawzes videos. I checked the pressure switch and it shows current so that should be fine. I can find no leaks. I put one of those parts house can gauges on it and it read less than 15psi when clutch was engaged and about 55 when stopped. So put another can in it until it was at 30psi while clutch spun. Still nothing. I hear a bit of a hissing sound from the neighborhood of the dryer/evaporator, but can't quite locate its specifc origin, but it just sounds like a normal a/c sound. I pulled the cabin air filter and felt the evaporator and it's no colder than ambient temp. The small line from the dryer is getting hot like I think it's meant to and all of the other lines from the expansion valve are ambient temp as well. I am afraid to keep putting refrigerant in it because I found an international check sheet online last night that may suggest(if I read it correctly) that I may be overcharging it. As I have never noticed a leak before, I can't image it is that low and 24oz later I'm afraid I'm going to pop the safety valve on the compressor. I don't have 1500 dollars to throw at snotty shops that want to just replace everything so I am hoping for some help ASAP. Please??!!
     
  7. RSQ20

    RSQ20 Medium Load Member

    Quit guessing, refer to post #2..

    ... Philip
     
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  8. jkgillian

    jkgillian Bobtail Member

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    Sep 27, 2009
    Hohenwald, TN
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    I know the pressures. They are mentioned in the post! (At least on the low side of the system) who carries a set of manifold gauges around? Those things can be pretty expensive.
     
  9. RSQ20

    RSQ20 Medium Load Member

    You do not know the pressures, just a low side is not enough..

    If you do not understand how the system works, you are testing fate... BOTH Hi/Low are required for correct diagnosis.

    That is like checking the tire pressure on the tractor and not the trailer...

    ...Philip
     
  10. Jphelps

    Jphelps Bobtail Member

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    Sep 23, 2017
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    Changed misters pulled it down recharging im at 32 low 170 high but it's not blowing ice cold should I put some liquid , turn bottle up
     
  11. Heavyd

    Heavyd Road Train Member

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    Feb 4, 2009
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    What did you charge it to?
     
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