A/C question

Discussion in 'International Forum' started by earnies2, Apr 14, 2021.

  1. earnies2

    earnies2 Medium Load Member

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    May 17, 2012
    Dedham, MA.
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    I just fixed my a/c and it is giving me
    40-42 degrees at the vent...the problem is when I come to a stoplight it makes a sound like a horn blowing. I traced it to the expansion valve. If I turn on my engine fan it stops. I didn't have my gauges with me to check the pressures and I only put 2.5 lbs in the system.
    Any ideas?
     
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  3. kemosabi49

    kemosabi49 Trucker Forum STAFF Staff Member

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    You say you "fixed" your a/c. Do you mean you fixed a problem like a compressor and bad o-ring somewhere, then evacuated the system and refilled it. Or did you just add some Freon until it started working?
     
  4. skallagrime

    skallagrime Heavy Load Member

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    Get it properly vacced and filled to capacity, you only put 2.5 lb in, my system takes 4.2, yours may take less or more than what youve got.

    That said, sounds like the valve is perhaps open too far or your pump cant keep up
     
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  5. earnies2

    earnies2 Medium Load Member

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    I had a leaking Schrader valve so I changed that. Whal it was empty I also changed the thermosters because they were almost 2 years old and I knew they would fail at the worst time. I also changed the fan switch because it looked like it was the original. I vacuumed the system down it held vacuumed overnight. then I gassed it with 2.5 lbs of 134... it is running fine only getting the horn sound at idle but if I turn my fan on it goes away.. I need to put my gauges back on and recreat the problem and see what they say
     
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  6. earnies2

    earnies2 Medium Load Member

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    I did vacuumed it out and it held overnight the system in the International prostar takes 2.5 lbs of 134A. If the valve was open to far wouldn't that affect the temperature at the vents? I'm getting 40-42 at the dash?
     
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  7. skallagrime

    skallagrime Heavy Load Member

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    If it were wide open yes i would guess it would not cool quite as well, but as long as youre building liquid before the exp valve it woupd still cool at least somewhat.

    Since turning on the fan fixes it at idle, my inclination is that youve got gas hitting the expansion valve at idle no fan, that points to slight undercharge or your compresser not QUITE keeping up at low rpm. The fan "fixes" the problem by cooling the gas just enough to flip it enough to a liquid

    Option 1, your new exp valve is just poorly designed and noisy
    Option 2
     
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  8. Rideandrepair

    Rideandrepair Road Train Member

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    International HVAC, I’ve been told are a bit different. I’ve never worked on one myself. My Shaker takes 55 Oz. I usually put 5 cans, or 60oz. Bleeding the line of air after hooking up each can. Works good for Me. Don’t know what thermosters are. Temp sensor Probe goes into evaporators maybe? Noise from an expansion valve usually means it’s sticking, sometimes mine makes noise when system is low. Sometimes it just makes a little noise, it’s normal. But a honking sound? I don’t know. Maybe you need to add some oil to the system. Though you shouldn’t have lost much, most should have stayed in the system. Whole system shouldn’t need more than 2oz. ( guessing) at 7% oil ratio, if my memory serves Me, 7% is the suggested ratio. Too much oil is worse than too little. It affects the cooling of compressor itself, making it run hotter, shortening it’s life, by displacing refrigerant. Having said all that, maybe add an ounce of oil with green dye, if dye isn’t already present. Shouldn’t hurt anything. 2.5 sounds low, I’d double check that with the Dealer. Noise going away with fan on suggests it’s a high pressure problem, yet if it were, fan should come on automatically. New fan switch, what about high pressure switch? The compressor should cycle off, while idling, and fan should come on, till pressure drops. Then fan goes off, compressor cycles on again. With fan engaged at idle, compressor may or may not cycle at all. Usually still cycles off, but stays off for a shorter time. I usually watch the operation at idle for a while. Making sure the compressor stays on longer than off. Ideally twice as long, on the hottest most humid days. If it doesn’t cycle off with a full charge, high pressure switch isn’t working. Don’t know what kind of switch you have. Could be a single or a bianary switch, part of the fan switch, essentially a double switch, that either side can go bad, while other is still working. You can figure that out. Lastly, a new dryer should have been installed. Old one may be full of moisture, from shrader valve leaking, or simply having the system open. A tiny amount of moisture can freeze up and jam the expansion valve. If it sticks, sometimes you won’t get cold air. Usually it’s cold, till valve freezes up, and iced over. Then it stops blowing cold, till you turn the system off, and let it defrost. And sometimes the valves just get sticky, and need replaced. Old ones will still look like brand new inside. Can’t diagnose one by looking at it. I’ve had them freeze up, from being sticky and eventually start working properly, simply by turning the system off when frozen, and on again. I suspect the moisture eventually got filtered out by the dryer. You can try that first. Instead of turning the fan on, turn the system off, when the noise is heard. Might just free up a sticky valve, if that’s the problem.Maybe a real mechanic who’s seen the problem before, and familiar with Internationals will chime in. Good Luck
     
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  9. Rideandrepair

    Rideandrepair Road Train Member

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    I agree with you. Mine is currently about 10 Oz low. It’s blowing ice cold, mainly because compressor running almost constantly. I know when it gets real hot outside, it won’t be able to keep up. That last can takes a long time on mine, Lol. I also noticed some more than normal noise from the expansion valve, along with some occasional icing of the a/c line. Cause - too low.
     
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  10. bad-luck

    bad-luck Road Train Member

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    I am not sure what you fixed. But anytime you open up the ac system you need a replace the ac dryer and orfus tube or the expansion valve if you have it. I recommend you get it done correctly.
     
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  11. bad-luck

    bad-luck Road Train Member

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    This is mine at the vent IMG_3193.jpg IMG_3193.jpg
     
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