Air Conditioning Quits Blowing Hard at Highway Speeds

Discussion in '1st Gen - 1997 - 2002' started by Josh1986, May 27, 2018.

  1. johnboneske

    johnboneske Full Access Members

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    the dripping water is just condensation... Over pressure would make it blow warm, and cycle the compressor frequently! Even when it working properly. I have it too.

    Did you try selecting another position of the fan like floor or defrost for 30 seconds and then back to dash vents, did it work?

    I will try the check valve, where is it located? Happen to be able to take a pic of it?
     
  2. swagfu

    swagfu Full Access Members

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    The check valve on mine is on the passenger side of the truck toward the firewall. If you follow the vac line from the the battery area, you will see it about a foot or so up the line. If I get time tomorrow I will take a pic and post it for you. In the meantime, here is a picture I found on the net. maxresdefault.jpg
     
  3. Josh1986

    Josh1986 Member

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    I selected different positions and it helped a little bit, but not enough to write home about.
     
  4. swagfu

    swagfu Full Access Members

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    Here are some pics from my truck.
    This is a pick of the valve right behind the battery.
    20180610_162153.jpg



    This one shows the vacuum canister behind the battery. I haven't removed it, but I think it is attached to the battery box. Not 100% sure on that though.




    20180610_162213.jpg


    Here is a view of the vacuum canister. I can't remember where I bought it from...ebay probably, but it included the valve in question.



    20180610_162354.jpg

    Close up of the valve.

    20180610_162401.jpg


    Part number for the canister.

    20180610_162441.jpg


    Hope these pics help you out. Let me know if you have any other questions.
     
  5. CHRIS HODGE

    CHRIS HODGE Member

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    Your a/c evaporator coil is freezing up, like stated above, with control in max position your not introducing any warm outside air into return. This allows the coil to slowly ice up and loose air flow. Try leaving air switch in normal and with age of unit evaporator coil may need cleaning.
     
  6. johnboneske

    johnboneske Full Access Members

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    you know that isn't correct... I never have to run my AC on MAX. It blows COLD! I can run it on low or one step up on my auto controls. If we both, who we both have the same problem shut off the AC for a minute or two and then restart it, the AC blows cold out of the dash vents again, which isn't even close to enough time for the coil to thaw, which tells you the coil isn't froze, plus the only reason a coil freezes up is either A: low charge on the refrigerant, or B high humidity. The point of an AC system is two steps: to lower the air temp and to dehumidfy the air.

    Yes my AC is at the proper charge level. I did it myself and am both HVAC Certified and EPA Certified for refrigerant... The reason it quits blowing out of the dash vents has nothing to.do with the AC charge, at least in my situation...
     
  7. johnboneske

    johnboneske Full Access Members

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    I was wrong! We were on a 550 mile trip today and it happened about 4 hours into our trip. I tried all my ideas and got the "typical" answers/what works for a short time. After it annoyed me for awhile, I turned off the AC but let the fan run, the air stayed cold for awhile and eventually warmed up, while continuing to blow harder without me having to turn up the fan speed... Which shows you were right! The coil is freezing up inside, so blowing warmer air past it, melts the ice, turns to water and of course melts which allows more air. Thanks!
     
  8. CHRIS HODGE

    CHRIS HODGE Member

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    Glad it is working for you, been working on A/C systems for 30 some years, but always learning new things.
     
  9. johnboneske

    johnboneske Full Access Members

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    I do residential and commercial AC/HVAC too... And of dabble in Auto, of course. I have never known of a inside coil to freeze up! We did a 1200 mile round trip road trip this weekend...

    What I did was when running the AC and noticed that the air wasn't blowing as hard or very limited, I would turn off the AC, and let the fan continue to run. Which after about 2 minutes the air flow would return and I could turn back on the AC and all was good, until it happened again... Then repeat the steps.

    Usually my AC was good for about an hour or so, the go through the procedure and all kept working. Thank you!
     

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