05 379 A/C question

Discussion in 'Peterbilt Forum' started by Cajuncowboy654, Jul 21, 2019.

  1. Cajuncowboy654

    Cajuncowboy654 Light Load Member

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    So I hooked the gauges to my A/C on my 379 as it doesn't seem to be as cold as it should and also temp seems to vary especially when parked.

    I had A/C on high recirculate in the truck, the gauges would climb to 48 on the low side and 300 on the high then the fan kicks on.

    Once it kicks off gauges drop to around 20 and 100, then the compressor starts, runs around 4 seconds then cuts off. Does this 5 or 6 times the turns on until the pressures build to 48 and 300 again.

    While the compressor it cycling on and off the low side will climb to around 40 but the high stays at 100. Gauges never seem to stabilize just constantly climb to kick the fan on. Outside temp is 77 degrees.

    Am I low on freon or something else possible or any other info I can give to help get an answer?
     
  2. truckdriver31

    truckdriver31 Road Train Member

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    07BB907F-9AF6-4292-B8BB-7D69EFD8BC48.jpeg
     
    Dunkin Wood 89 Thanks this.
  3. truckdriver31

    truckdriver31 Road Train Member

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    these charts can help you. they are only a starting point and only a reference.
     
  4. Cajuncowboy654

    Cajuncowboy654 Light Load Member

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    I have those charts, found them online.

    The issue I'm having is it never really stabilizes to get a reading or do I look at its lowest point or highest point as the reading?
     
  5. truckdriver31

    truckdriver31 Road Train Member

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    you look at both. if its cycling off and on too fast. then its low and you have a leak
     
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  6. Diesel Dave

    Diesel Dave Last Few of the OUTLAWS

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    Does your A/C system have an eye glass on the dryer ? If so, that’s what I would go by. Once the eye glass is clear, it’s full.
     
    Cajuncowboy654 Thanks this.
  7. pushbroom

    pushbroom Heavy Load Member

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    Whats the last 6 of the s/n. If you have a scale I can tell you exact charge.
    Is the low pressure switch cutting off the compressor? Also the above charts only read correct with the fan locked on. Other wise high side pressure will climb to kick the fan, come down and repeat.
     
  8. Cajuncowboy654

    Cajuncowboy654 Light Load Member

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    Ok so found an issue before I can test properly. The fan override switch in my cab doesnt lock the fan on.

    Any idea what could cause this. The fan acts normally otherwise just wont lock in with the switch
     
  9. truckdriver31

    truckdriver31 Road Train Member

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