a/c

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Superhauler, Jul 27, 2016.

  1. Superhauler

    Superhauler TEACHER OF MEN

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    No I made sure of that.
     
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  3. AModelCat

    AModelCat Road Train Member

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    Typically the compressor clutch is controlled by the high, low and thermostatic switch. I'm just thinking out loud here. Low pressure switch should keep the clutch from activating from low ambient temps or low charge. High pressure switch is a safety to prevent excessively high pressures. Thermostatic switch should open when the evap core cools to just above freezing. Now you say all 3 are new and the clutch disengages when you turn the A/C off. That should rule out a short to power in the clutch circuit. Without having the truck in front of me my guess would be that maybe there is an issue with the thermostatic switch in the core. Cuts and sharp bends can damage the probe and the switch won't work right.
     
  4. Superhauler

    Superhauler TEACHER OF MEN

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    I dont think it is the issue. It was freezing up with the old one also.i made sure to not bend it to sharply. I think the next time I get in I will run the wires out some more and hook the old one up and move the points with a screw driver and see if the compressor kicks out. If it doesn't then there is a bad conection under the dash somewhere.
     
  5. Bean Jr.

    Bean Jr. Road Train Member

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    A truck I drove 6 years ago had an a/c problem. After changing all the switches, the mechanic thought it might be in the loom, so he bypassed it, but forgot to wire in the tthermostat, so it iced over. He wired in the thermostat, then it worked well.

    Maybe there is a broken wire for the thermostat?
     
    magoo68 Thanks this.
  6. Superhauler

    Superhauler TEACHER OF MEN

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    That is what I'm leaning toward.
     
    Bean Jr. Thanks this.
  7. philv

    philv Light Load Member

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    It's a plugged evap. Just went over this in class today. If your evap can't collect heat by air going through it then the evap outlet (suction line) will freeze up.
     
  8. Superhauler

    Superhauler TEACHER OF MEN

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    Plugged? As in dirt plugging the fins? Or the lines plugged? It has been cleaned. I removed it and had a rad shop boil it. The only thing I didn't do was the heater core. It looked good. But since they both use the same air flow maybe it is the culprit.
     
  9. Skate-Board

    Skate-Board Road Train Member

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    I think it's the trinary switch on top of your air dryer. That's what controls the compressor turning on and off based on pressure.
     
  10. Superhauler

    Superhauler TEACHER OF MEN

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    Mine doesn't have that on the dryer. Just a high and low pressure switches in the line. Both were replaced, didn't solve it.
     
  11. philv

    philv Light Load Member

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    Yeah the fins. It shouldn't be the heater core cause the plenum should have a blend door that blocks the air flow from it when you want a/c.
     
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