a/c in a different vehicle

Discussion in 'Heating & Cooling' started by powerboatr, Aug 30, 2018.

  1. stamp11127

    stamp11127 Super Moderator Staff Member

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    The high side is a little worrysome. The safety will lift on the compressor @450 psi, you shouldn't be anywhere near that. The normal pressures we are seeing here in Ga. are 35-37 on the low and 220 on the high side once the system has stabilized. The high pressure switch may be cycling the compressor on and off. If it is then you have more work to do, it may be as simple as being slightly overcharged.

    How long have you let the system run?
    At what pressure will the compressor cycle off & on?
    What is the static pressure after sitting idle for 30 minutes or more?

    Pressure chart for r134a:
    http://acprocold.com/faq/r-134a-system-pressure-chart/
     
  2. powerboatr

    powerboatr Full Access Members

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    static after shut down took about just a few minutes if that long to bring both sides down, iirc it was around 60 on both sides, but i didnt log it,
    it was equalizing, then if i restarted it ran in the range , took a minute to get to 44 , it would get to 40 pretty quick then slowly move up. The high side really stayed pretty steady within the range by the chart, 160 was the high for the event, that why i logged it. the range was 150 to 170 for temps. the temps though i question, as it was most certainly hotter around the area. the 0ver 400 was when the compressor shut off, it just sort of climbed slowly , then held , then dropped immediate once compressor was called back to run. the switching is at the drier which controls the condenser fan and the clutch engagement
    it was really very smooth and no huge pressure jumps, just making cold air
    actually it was SMOOTHER than it ever ran since 2009. that may sound weird, but the it was very stable and no weird behavior. no pulsing of hoses, no weird vibrations, no weird noise
    the tx valve got cold and frosty the low side got frosted, then the clutch would be called to shut off and the two would defrost.
     
  3. stamp11127

    stamp11127 Super Moderator Staff Member

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    Static pressure for r134a will usually be close to ambient temp. Since you read 60 that would indicate being low on the charge.
    Icing components also indicate a low service charge.
    We usually have higher high side pressure than you, also indicates a low charge.

    If your evap starts freezing up add more refrigerant - half ounce at a time. The high side will react faster than the low side. Occasionally check the static pressure and compare to ambient temp.
     
  4. powerboatr

    powerboatr Full Access Members

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    i concur that it may be a bit on low side, but am hesitant to add more until i get a good road check next week, waiting on a motor controller now so the bus is basically "on blocks"
    the label wanted 56 oz, i know i have by weight right at 58 in the system, but my weights could be off slightly to favor a lower number.
    my math shows the system probably should be 60 to 62 oz based on the extended suction hose they installed in 2010, it placed 4 feet and a loop over in the system to remove the torque pull under load and to clear the suspension and pinch points.
    i want to make sure i don't accidentally to overcharge.

    so getting up tp 65 mph and really moving some air and refrigerant at higher volumes than can be done at fast idle will dictate if i add more.
    being a slower rise in low side, does point me to add more. nothing beats a high load test
     
  5. gixer2000

    gixer2000 Retrofit or Bust Supporting Member

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    Tell me more about the switching near the drier for the clutch and condenser fan. I'm curious because seeing a 400psi head is insane and almost impossible if the compressor isn't running. 400psi=183°.


    Was just the suction line extended or the liquid line also? I'm asking because the suction line being extended won't change your charge very much but the liquid line will. Remember the liquid line should have a full column of liquid and suction line is mostly vapor so liquid line length being extended is way more important than the suction.
     
  6. powerboatr

    powerboatr Full Access Members

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    the switch on the drier controls the condenser fan and the clutch engagement. at least thats how it appears in the wiring schematic, but then again most the schematics i have are incomplete from damon so there could be another switch

    but yes once the compressor shuts off the high side climbed slowly up to 400 ...have no idea why, but everything i read says its possible
    then once the compressor came back on the pressure dropped right quick to the levels for the outside temps.
    suction line was extended.
     
  7. Dennis_H

    Dennis_H Well-Known Member

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    Could the High Pressure hose be routed too close to a heat source, like an exhaust? That may explain why temp goes up when compressor is off.
     
  8. gixer2000

    gixer2000 Retrofit or Bust Supporting Member

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    If that were the case your static suction would increase also and its not. It makes me question if there is an anti migration solenoid valve that is having the system pump down when it turns off. Solenoid valve would completely close the your liquid line causing an increase until the suction pumps down low enough to trip the low pressure switch. That's really the only thing that makes sense
     
  9. powerboatr

    powerboatr Full Access Members

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    beats me....
    if i get my slide room controller fixed this weekend i plan on a highway run to see whats what then see what the gauges indicate.
    now i am chasing a phantom 4 volt drop, across a motor controller, 3 brand new controllers and still the same result.
    if i jumper and by pass the controllers, its all 100% .
    and its only one side of the bus, but all 6 slides get power from same solenoid, but only two slides are acting up.
     

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