A/C not working after new parts.

Discussion in 'Interior' started by Merc1973, Jul 22, 2018.

  1. Merc1973

    Merc1973 Full Access Member

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    Installed a new Denso AC condenser since it was visibly leaking, new NAPA orifice tube and line, new 4-seasons accumulator, new rubber seals soaked in PAG46 and replaced appropriate PAG46 oil in each part today.

    Sucked down to 30 psi for 45 minutes, held. Put in 3.5 cans of r134a idling at 1500 rpm, compressor was sucking it in nicely. But the low side numbers stayed at 45-55, high side was 180-200. Then all of a sudden compressor just cut out, will not engage...

    WTF???? I feel defeated. Before i noticed the leak, A/C has always been freezing cold... Anyone got an idea?
     
  2. Merc1973

    Merc1973 Full Access Member

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    Update, after a beer to relax. I went out there, hooked up the gauges, the compressor runs, but But both are reading as if it low on freon. I put in another 1/2-3/4 can. Numbers look good, its cycling on and off, vent temp is reasonable but not like before. :mad:
     
  3. Merc1973

    Merc1973 Full Access Member

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    Go out again, numbers look low, must be a leak.
     
  4. SnowDrifter

    SnowDrifter Full Access Member

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    A point of note: Vacuum is not fool proof for detecting leaks. It pulls parts together, whereas under operation, parts are pushed apart

    Most oils have a UV dye in them any more. If that was the case with yours, poke at it with a blacklight. Will be fairly obvious
     
  5. Merc1973

    Merc1973 Full Access Member

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    Update. No visible leaks. I still have intermittent AC, cold when it works though. The compressure will shut off at 250 psi on high side, low side rhen goes up to 90 psi. If i turn it off the truck and restart like when getting gas AC won't work. Fan clutch "seems" to be working, when its hot in can spin the fan 2 to half turn. Should the clutch fan lock up at high temp?

    I installed a new AC Delco pressure switch at the accumulator and a new front cabin temp sensor in roofliner. I will try to recalibrate the HVAC system.

    Should i try to evacuate the system and try again?
     
    Last edited: Jul 7, 2019
  6. Merc1973

    Merc1973 Full Access Member

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    I really hate throwing parts at it. I need to clarify. I never did see the high pressure get to 250 the other day.

    Today during my commute home. AC worked cold for about 20 min of my 35 min drive then became hot. At home I Shut it off for about 15min and hooked up the gauges and the A/C worked for about 5 min. Then the compressor disengaged. The pressures were reading while working were L: 35-45. H: 150-175. Temp outside was 82. I thought those readings looked good...

    What is causing the AC compressor to shut off? Is the head unit bad? Would the exterior ambient temp sensors behind the grill be at fault? Im totally at a loss.
     
    Last edited: Jul 10, 2019
  7. SnowDrifter

    SnowDrifter Full Access Member

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    250psi high side is turning off the compressor so it doesn't blow up. Those pressures are way too high. What does low side look like when that's happening? Could be overcharged, heat saturation, or clogged/poorly flowing expansion valve
     
  8. Merc1973

    Merc1973 Full Access Member

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    250 is not too high esp on a hot day.

    http://rechargeac.com/how-to/ac-system-pressure-chart


    Problem is fixed. Turned out to be the compressor clutch air gap was too large. Here is a video that helped me figure it out. At 266k miles I'm not surprised.



    I had the same problems. AC would turn off...roll down windows it turns back on. Or AC turns off, turn in headlights it would turn back on... Extra power draw demand in system increased voltage to keep the electro magnetic clutch engaged. My air gap was quite large like this video. But since i had to remove the compressor ro remove shims i might as well replace it. Easy job through the passenger side wheel well.

    ACDelco 15-20941 GM Original Equipment Air Conditioning Compressor and Clutch Assembly https://www.amazon.com/dp/B000C984Z2/ref=cm_sw_r_cp_apap_63M6HH6HLku9I

    Hard to beat $158 for a New Denso AC Delco Compressor. Ice cold and doesnt turn off anymore. I do have to find a leak though that i found when system put under vacuum. I injected some dye, it's been ice cold for a month so far so I'm in no rush to find the leak.
     

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