R12 Expansion Valve with R134A charge?

Discussion in 'Technical' started by Jsarnold, May 25, 2012.

  1. Jsarnold

    Jsarnold Senior Member

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    I have the original (R12) style expansion valve in the Maverick AC system. The Wikipedia explanation for expansions valves cited in Frank's thread says that the gas inside the bulb in the metering valve is the same as the refrigerant in the system.

    Is that why expansion valves are specific to R12 or R134A? Anyone know what happens when an R12 expansion valve is used in a system charged with R134A?


    When I bought the under hood AC kit from Classic Auto Air I was told the old style (R12) expansion valve would be OK. My system does have one anomoly that I thought was related to the anti-icing switch in the evaporator but now I'm wondering if its a result of using the R12 expansion valve in a system charged with R134A.
     
  2. diddie

    diddie Member

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    Yes it will work with either Refrigerant! we convert older systems where i work all the time and they work fine
     
  3. Mavman72

    Mavman72 Gone backwards but lookin' forward

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    Jim...What exactly is the problem you are experiencing???
     
  4. Jsarnold

    Jsarnold Senior Member

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    The system works fine except, in very hot weather, the compressor cycles and the air coming out the outlets isn't as cold as it should be. I think the anti-icing switch (probably not the correct name) in the evaporator is switching the compressor off when there's really no danger of iciing.

    Someone on here said the switch is adjustable but I don't see how to get at it with the under dash heater/ac unit in place. Haven't been bothered by it enough to take the underdash unit down again. I checked out and replaced or renewed everything in it, EXCEPT that switch, when I had it out before and hoped to never pull it down again.

    That statement about the gas in the bulb in the metering valve got me wondering if the R12 vs R134A expansion valve might the problem. Guess not.

    I'm tempted to put a jumper with a toggle switch around the anti icing switch to see if it does ice up when the compressor runs full time in hot weather.
     
  5. Mavman72

    Mavman72 Gone backwards but lookin' forward

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    Insufficient air flow over condensor
    Over/under charged...
    you should stick a thermometer in a vent and see how cold the air coming out is...
     
  6. 71gold

    71gold Frank Cooper Supporting Member

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    I found that in the..Max...position on the control it will have the compressor running all the time. on...med...it cycles on/off...

    I am putting my old expansion valve back on today. I looked up the # on my new one and it goes to a...jeep/Renault...the old on goes to big rigs...Freightliner/Peterbuilt/Volvo/International all with sleepers...:huh:
    hope this isn't off your topic...

    ...:cool:...
     
  7. Jsarnold

    Jsarnold Senior Member

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    In hot weathe when it cycling I'll put the fan on hi. Don't you think the anti-icing switch could be opening too soon?

    When the compressor is running, the air coming out the vents will be in the low 30s.

    Charged the system with 24 oz of R134A as instructed by Classic Auto Air. Air coming out the vents was in the low 30s when almost all the 24 oz were in the system.

    If the system is under charged, and air out the vents isn't as cold, would you expect the compressor to be cycling?
     
  8. Jsarnold

    Jsarnold Senior Member

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    That's interesting!! Gotta think about that.

    Not at all. :rofl: I started to post to your thread but wasn't sure if my questions was sufficiently close to yours. Probably would have been better as one thread.

    Gotta go now but will come back to this later.
     
  9. blugene

    blugene Senior member Supporting Member

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    I can see where it would seem they would react differently.. I personally would keep it specific. Many variables that can affect the outcome. Altough the valve may work the same, how or who knows if the orfice is a different size? I understand the "expansion valve" is variable but it has a maximum and minimum opening.
    I remember back in the day when I was all into AC (and auto repaires in general), we had kits that had many different color "orfice tubes".
    MY opinion is if it works but changes with outside temps getting hotter, then I personaly would look to condensor cooling. Provided that the system has no leaks or bad clutch gap or other..
     
  10. Mavman72

    Mavman72 Gone backwards but lookin' forward

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    If the charge is low the compressor will cycle on/off in the max AC position. But as Frank stated... It cycles on off in med (or low for that matter)...Gotta tell ya. 30 deg is pretty cold...Systems generally run between 40 and 43 deg. Though I have seen em run as cold as 12 deg F. If the thermo switch is malfunctioning. The AC usually does not work at all.
     
  11. blugene

    blugene Senior member Supporting Member

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    Yes. And in this case it does sound like Frank got it. My opinion is only if it isn't the switch position being the cause..
     
  12. Jsarnold

    Jsarnold Senior Member

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    OK, I'm back. Thanks, everyone, for all the comments.

    When outside temp is mid-90s or above, I run the "Temp" control on cold, AC control on "Max", and fan on "Hi". That's when the compressor is cycling and air coming out the vents (good air flow) isn't as cold as it should be.
     
  13. darren

    darren Member

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    Low 30's??? With it being that cold I would think your in danger of freezing up the evap and dropping the airflow. Thats awfully cold.
    Done tons of r12 to 134 installs. Never switched the H-valve unless it was failing anyhow.

    Norm on hot humid days here is in 40's and 50's at the center vent. 30 is really cold.
     
  14. Jsarnold

    Jsarnold Senior Member

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    That's a big surprise to me. I expected if the charge was low the compressor would run constantly but just not cool well. Maybe I should try adding 2 or 4 oz of refrigerant?

    I would expect the compressor to cycle if the fan is on med or low.
     
  15. Dave B

    Dave B I like Mavericks!

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    If it has a low pressure switch, it will cycle the compressor (clutch) when the pressure is low to prevent freezing, and compressor damage. Cycling the fan would just lower the pressure, if you could stop the condenser fan, you could raise the head pressure, in turn raising the suction pressure, and that would prevent freezing, but Mavericks aren't that fancy.
    It in olden days, when I worked at a Refrigeration shop, we'd charge cars out the back door, and we were told to keep throwing the refrigerant to them until the clutch stayed in.
     

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