AC system is acting up

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Oscar the KW, Aug 17, 2014.

  1. Oscar the KW

    Oscar the KW Going Tarpless

    12,246
    28,113
    May 19, 2011
    0
    Driving down the road sometimes it works perfect, sometimes it will only pull the temp down to 5-8 degrees below ambient temp, and doesn't do a good job at pulling the humidity out of the air.

    Sitting still, I will stay nice and comfortable. But, this afternoon it was in the upper 80's, I put a produce thermometer in the vent and watched the temp. It would normally stay at 57 degrees, once in a while it would run up to 65 degrees, and sometimes it would pull down to 40 degrees. All these temps were with the temp selector on the dash in the same position, water temp was constant thru out.

    For whatever reason, it seems to be worse at highway speeds, with the engine fan on, or heading into a headwind.

    I have checked every electrical connection for the system under the hood, everything there seems to be kosher.

    Thoughts?
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. 6 Speed

    6 Speed Heavy Load Member

    945
    482
    Jan 2, 2014
    0
    Filter?......
     
  4. rickybobby

    rickybobby Road Train Member

    4,843
    6,672
    Jul 10, 2010
    greensboro, nc
    0
    I have the same problem. I stop and turn truck off, then back on it works fine. The problem comes and goes, it doesn't happen all the time
     
  5. wore out

    wore out Numbered Classic

    14,322
    173,740
    Jun 5, 2013
    CHASIN THE DEVIL'S HERD
    0
    Do you have a sight glass in the drier? They are usually right in the top of the drier, most of the time they still have the masking tape covering the glass from when the drier was painted at the factory. It kinda sounds like low freon level but putting a can in can be the wrong thing to do if it isn't low. If you have the sight glass if its real foamy then its low. If its mostly clear with a few bubbles then its ok.
     
    Oscar the KW Thanks this.
  6. Verdel

    Verdel Medium Load Member

    586
    129
    Oct 26, 2013
    0
    Open the hood with engine running at about 1000rpm and AC On. Watch the Ac compressor clutch, if it is engaging. If the clutch is on and off rapidly - you maybe low on freon. Second test is when you driving down the road, if you see the AC is blowing warm, stop the truck open the hood without shutting the engine off and see if the AC clutch is engaged, if not knock on it with a piece of wood or something and see if the clutch engages, if it does - it means you need a NEW AC Compressor. You can try to add some freon first and if does not work, change the compressor with a new dryer.
     
  7. Oscar the KW

    Oscar the KW Going Tarpless

    12,246
    28,113
    May 19, 2011
    0
    Can't really see anything in there. I took a flashlight and shined it down in there, looks like you can only see about an 1/8", and its clear.

    When sitting clutch cycles normally, if I am going down the road and its not working properly, come up to a stop sign and before I even get stopped it will be blowing cold.
     
  8. Pool6710

    Pool6710 Medium Load Member

    662
    257
    Aug 10, 2014
    Minnesnowta
    0
    Hook a gauge up to the ac and make sure it's charged. I had to throw a can in mine this year and it's been cool since.
     
  9. wore out

    wore out Numbered Classic

    14,322
    173,740
    Jun 5, 2013
    CHASIN THE DEVIL'S HERD
    0
    Since the sight glass is mostly clear, I would say freon is ok. If your drier has the stem on it with the color stem (looks kinda like a sight glass) blue is ok white is bad. It kinda sounds like there is blockage between the condenser and evap core. Since your system hasn't been open that points to maybe the drier is stopped up or the expansion valve or orafice tube is stopped up depending on what you have. What the blockage does is cause the low side to actually pull into a vacuum as air runs across the condenser to lower what should be rising pressure from freon chaning from liquid to gas. The low side falling that quick is what kicks the clutch out due to low pressure switch. It may be best to get it checked ASAP as when a compressor comes apart it can be a nightmare afterward. Again I can't be sure without seeing touching and feeling but its just what it sounds like.
     
    Oscar the KW Thanks this.
  10. Oscar the KW

    Oscar the KW Going Tarpless

    12,246
    28,113
    May 19, 2011
    0
    I'm thinking that's the kind that I have, looks like a really dark blue to me.



    I've never really dug into how an AC system does what it does, but I did a real brief search on expansion valves, and I am thinking that it could be that. Last week the AC acted up as I described above for the first time, I ran 500 miles to home after getting empty it worked flawless, left home and ran 400 miles to reload and it worked flawless, loaded and drove 510 miles and again, flawless, 340 miles yesterday and it didn't work for beans, unless I was just going slow thru a town under low RPM.
     
    wore out Thanks this.
  11. Oscar the KW

    Oscar the KW Going Tarpless

    12,246
    28,113
    May 19, 2011
    0
    I don't have a gauge to put on it, but I will get one in the future to help narrow things down.
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.