Non IH Tractor A/C question

Discussion in 'Tractor Tech' started by kevingweq, Feb 5, 2018.


  1. kevingweq

    kevingweq High Wheeler

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    I know it's not IH but Landini and McCormick are now in bed together :1eye:
    Landini Mythos 100 tractor ,fairly modern HVAC system 2012
    New GM (Delphi) v5 compressor ( rotary piston type w/variable displacement ) displacement controlled by compensating valve on compressor (not electric)
    New filter/drier, original TXV valve ( not orifice tube style)
    Evaporator,condenser, heater core are all clean (inside and out)
    Ran vacuum pump for 1.5 hrs , vacuum held steady overnight
    System calls for 47 ounces R134 and 8 ounces oil , Charged it up
    Static pressure after sitting overnight is 67.5 psi at 60deg ambient
    When running 5-10 mins Low side 26psi High side 125psi
    It cools VERY good very quickly Evaporator temps are in the 20's
    Should I be concerned with the high side pressure being this low ?
    The manual calls for @ 60deg (min)135psi (max) 185psi
     
  2. Dana Strong

    Dana Strong Y-Block King

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    The listed pressure of 134A at 60*F is 58 psi. so I might wonder if your gauge could be off a bit. I haven't worked with that refrigerant so don't know much about its performance or quirks, but would ask what was done to the system since it was new? Any major changes, what is its operating history, or anything else which might be pertinent to the situation?
     
  3. Greg R

    Greg R Dreams of Cub Cadets

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    Without knowing the ambient temps, engine rpm, or cabin temps, it's very hard to say. It's just numbers with no reference. It looks close but the evap temps should be above freezing which will put suction pressure around 28-29 psi minimum. A system short on charge will have evaporator icing in no time. With an 80* day and a cabin temp in the 70s, I like to see evaporator discharge air temp in the mid 50s and going lower. Head pressure for the same condition will be close to 180 - 210 psi. One ball park number I like for head or discharge pressure is 2.2 to 2.5 times the ambient temp for a close to head pressure reading. Engine rpm is 1,200 to 1,500 rpm for good compressor pumping.

    You shouldn't have a deep standing vacuum for more than 15 minutes with the pump blanked off. Letting it set overnight does nothing but potentially allow air (moisture) in. If the vacuum pump is running then it's okay, but just to set while valved off is inviting problems down the road.

    If performance is poor with high discharge pressures and very hot at that, then there's air still in the system.
     
  4. kevingweq

    kevingweq High Wheeler

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    60-65 deg F (shop temp)
    1200 rpm

    Mid to high 20's is actual eveporator temp while running (infrared temp gun reading )
    cabin temp will drop into 40's

    Both the gauges seem to read the same ( within a pound)

    Original system had approx 4000 tractor hrs on it , mostly summer time field work
    Complaint : No A/C - No Heat, Found mud clogged evaporator , Low charge ,
    Clean and flush system ( inside and out ) Compressor would not make more than
    80 psi
    New compressor , New Drier ,

    I am going to try to partially block the airflow over the condenser to load the compressor a bit more ,
    My thinking is that the system is running too efficiently and cool to work the compressor hard enough .
     
  5. Greg R

    Greg R Dreams of Cub Cadets

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    Wait until summer. For me it looks pretty close, there just ain't enough load with everything at an ambient of 60*. Mobile a/c is a different animal from stationary a/c. What you don't want is blowing a high side hose, or tripping a high pressure c/o switch in a hot summer because someone tried for a target discharge pressure in the winter; a common mistake with stationary 608 guys.
     
  6. Dana Strong

    Dana Strong Y-Block King

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    Just curious what this is from; dust from outside getting drawn into the cab and settling on/mixing with condensation there? Is there any way you can periodically check and clean it easily in the future? Does your soil ph tend to run 8 or higher? If so, that might at least inhibit formicary corrosion.

    Greg; any opinion about "Static pressure after sitting overnight is 67.5 psi at 60deg ambient"? According to my tables, this is about 10 psi high. All the systems I've worked on had static pressures pretty close to the correct values unless there was contamination by other refrigerants, air, or breakdown products.
     
  7. Greg R

    Greg R Dreams of Cub Cadets

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    The correct temp/press relationship has to be at saturated conditions or in another words, there has to be liquid in the system or container with no separation of valves or devices between them.
    The static pressure variation brings up the point of a standing vacuum overnight, it could possibly be non-condensables or maybe all vapor; then again the proof will be when it's running at capacity.
     
  8. kevingweq

    kevingweq High Wheeler

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    Thank you for all your input Greg , I put a couple pieces of cardboard in front of condenser and sure enough
    the pressure went right up to 175 psi, removed it , dropped back down to 125psi ,
    System calls for 47 ounces refrigerant and that's exactly what was installed , Hopefully manual was correct .
    It called for 0.240 cc of oil in entire system , I figured they had to mean 240 cc or 8.1 oz

    Part of my concerns stemmed from a consistently poorly translated manual ,,,,, example in chart below re: LP Gauge pressures on R134A chart
    landini manual chart.jpg

    The design of the fresh air intake leaves much to be desired , It incorporates a substantial intake dust/ chemical charcoal filter
    but the air intake is just a simple mesh screen flush with the top of the hood , Rain water or wash water easily flood into
    the "air box" and flush the dirt straight into the evaporator , It is NOT easy to service :1eye:

    This was the condition of evaporator , No wonder the compressor lost it's jewels
    landini ac condenser 001.jpg

    The 2 lower openings in firewall are where the evaporator resides , the 2 upper ports are recirc air from cab
    landini ac box 002.jpg
     
  9. kevingweq

    kevingweq High Wheeler

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    Dana I had to look up the term "formicary corrosion" At first I thought you were wondering if the tractor was infested with ants :1eye:
    But then I learnded sumthing new , Thank You
     

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