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Ac question

Discussion in 'International Forum' started by earnies2, Oct 8, 2019.

  1. Oct 8, 2019 #1
    earnies2

    earnies2 Medium Load Member

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    May 17, 2012
    Dedham, MA.
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    I'm not sure what this is when I slow down I hear a noise like a horn blowing in the passenger side dash when I put my engine fan on it goes away....that's why I think its ac related...any ideas?
     
    earnies2, Oct 8, 2019
    earnies2, Oct 8, 2019
    #1
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  3. Oct 8, 2019 #2
    snowwy

    snowwy Road Train Member

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    Are you running the ac or not. The engine fan shouldn't really have anything to do with the ac. Except when it's needed to lower the high pressure in the condensor.
     
    snowwy, Oct 8, 2019
    snowwy, Oct 8, 2019
    #2
  4. Oct 9, 2019 #3
    earnies2

    earnies2 Medium Load Member

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    May 17, 2012
    Dedham, MA.
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    The prostar dosen't have a ac on off switch? Even if not on ac but the dial is on the blue range I would assume the AC is running? The noise is coming from the AC area. I will duplicate the noise and investigate further. This noise started after I changed the compressor,receiver, and expansion valve...
     
    earnies2, Oct 9, 2019
    earnies2, Oct 9, 2019
    #3
  5. Oct 9, 2019 #4
    snowwy

    snowwy Road Train Member

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    Everything has a on/off for the ac somehow.

    When 134 came out. High pressure switches were installed. 1 to kick the fan on when hi pressure got to high. Another to shut the compressor off if high pressure got to high.

    134 originally ran at much higher pressure then 12.

    It's not much higher then 12 these days.

    I'm not sure how many brands use 2 high pressure switches anymore these days. Since the ac is tied into the BCM.

    You can actually read the pressure with obd system also. Least my new car can read using app on my phone.
     
    snowwy, Oct 9, 2019
    snowwy, Oct 9, 2019
    #4
  7. Oct 10, 2019 #5
    earnies2

    earnies2 Medium Load Member

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    May 17, 2012
    Dedham, MA.
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    Ok today I had the AC on and the truck was idling and it made the noise the fan wasn't turning so I taped on the high pressure switch and the fan came on after about 10 seconds the noise stopped
    I think I will replace the high pressure switch....
     
    earnies2, Oct 10, 2019
    earnies2, Oct 10, 2019
    #5
  8. Oct 10, 2019 #6
    snowwy

    snowwy Road Train Member

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    The fan won't come on till hi pressure gets hi enough. You tapping on it just happened to be a coincidence. At the right time.

    If you're driving down the road. The fan will never come on. ONly when you're idling. Or going slow enough does the fan come on.
     
    snowwy, Oct 10, 2019
    snowwy, Oct 10, 2019
    #6
  9. Oct 10, 2019 #7
    earnies2

    earnies2 Medium Load Member

    690
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    May 17, 2012
    Dedham, MA.
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    That seems to be the problem the fan isn't coming on when I slow down?...
     
    earnies2, Oct 10, 2019
    earnies2, Oct 10, 2019
    #7
  10. Oct 10, 2019 #8
    snowwy

    snowwy Road Train Member

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    It's not something that happens immediately. And if you're in colder temps. It will take longer to hit hi pressure.

    Your compressor will shut down if the pressure gets too high.

    The best way to really diagnose. Is to have gauges on the truck. Without those. You're thinking blindly.
     
    snowwy, Oct 10, 2019
    snowwy, Oct 10, 2019
    #8
  11. Oct 10, 2019 #9
    earnies2

    earnies2 Medium Load Member

    690
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    May 17, 2012
    Dedham, MA.
    0
    I realize that but I don't have my gauges with me and I don't want to loose my AC until I can get home....
     
    earnies2, Oct 10, 2019
    earnies2, Oct 10, 2019
    #9
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