2015 Volvo 670 AC problem

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by pete159, Apr 27, 2021.

  1. pete159

    pete159 Light Load Member

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    Dec 6, 2008
    mississauga
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    I've been driving 12 years and it seems like I've never had an AC system that has always run perfectly. The current issue is it will seem like it's working okay but as I'm driving along it blows less and less powerful. I turn off air circulation and then it will possibly start blowing harder sometimes I will turn the AC off with the fans all the way up and it will again start blowing harder at which point I turn AC back on. During the night the AC blows less and less both in the cab and the bunk until it's hardly blowing at all but you still feel cold air. The blowers are fine and the cab one was replaced about a week ago.
     
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  3. Snailexpress

    Snailexpress Road Train Member

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    Looks like you have icing issue. If AC charged not properly it will freeze too much and ice will form over evaporator fins. Thermistor (sensor) for freezing mounted directly on the fins should sense ice and prevent buildup.
     
  4. pete159

    pete159 Light Load Member

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    Dec 6, 2008
    mississauga
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    So you think it's either not enough magic gas or too much?... Should I pull into a truck stop and have them do a leak test and see how much Freon I have? This truck is had ####loads of AC work done on it over the last year over $2,000 and still not working right
     
  5. Snailexpress

    Snailexpress Road Train Member

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    You can check refrigerant with cheap Walmart bottle. Check water drain from AC unit. How is sleeper AC working?
     
  6. baha

    baha Road Train Member

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    Next time you pull over and its not blowing hard, shut off the truck wait for a few min and watch if a lot of water starts running under the truck where a/c drain tube runs out, if it starts pouring out after a few min. you must replace the temp control sensor that lives inside a/c heater box under dash that not working ?
     
    Last edited: Apr 27, 2021
  7. pete159

    pete159 Light Load Member

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    Dec 6, 2008
    mississauga
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    Okay I'll test for leakage. The bunk will have the same problem.. I woke up suddenly and it was hot as hell but then I cranked the bunk fans to full and after a few minutes it was blowing hard and cold, when I went to bed it was on low and blowing soft and cold and fine. I went into the front bunk and it was #### hot I had to turn off circulation and crank it and after a couple minutes it started blowing cold.
     
  8. BigNutTurner

    BigNutTurner Bobtail Member

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    Apr 20, 2021
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    I'd agree with the icing diagnosis. One easy thing to check as well is your cabin air filters. If the filter or ducting doesn't flow like it should then there isn't enough heat transfer from the evaporator to the air being fed to the vents. This causes the evaporator to ice over and restrict airflow and you'll have warm air blowing out of the vents.
     
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