AC problem, no power to AC compressor

Discussion in 'Western Star Forum' started by 04 LowMax, Jul 7, 2014.

  1. 04 LowMax

    04 LowMax Medium Load Member

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    Feb 3, 2013
    Alberta
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    Wondered if anyone has done any trouble shooting for this problem on a star? Was all prepared to head to a shop and get ac recharged, then thought I better just make sure the compressor is working. Good thing I did, it wasn't. No 12 volts at comp plug. Went to heater control panel, have 12 V at ac switch, (with blower on) and so switch is sending it down the line but where it goes to, I don't know. Can't find any fuse or breaker labelled AC. Tried running a separate set of wires directly to ac comp, it kicks in fine, draws 3.2 amps. Plus you can hear it snap in when it gets power. So just wondering if anyone has found the path of the power circuit from in the cab to the ac compressor?
     
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  3. snowwy

    snowwy Road Train Member

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    put gauges on system. if there's no freon. there's also no voltage to the compressor.

    you need at least 50 lbs freon before the compressor will kick on. think, low pressure switch staying off.

    find the low pressure switch, it'll be on the line with the blue cap on it. if you still got it. it's the thicker tube. check for power at the plug. if there's power. take a paper clip or something to stick in the plug at both terminals. see if the compressor kicks on. you don't need the engine running,. you will hear and see the compressor clutch engage if there's power supplied to it.

    you might have 2 high pressure switches. one kicks the fan on if the pressure gets to high. the other also shuts the compressor off. if pressure gets too high.
    never been in a star so i have no idea if there's 2 switches or not. on the high side.
     
  4. jbatmick

    jbatmick Road Train Member

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    Let's talk about this for a minute. 50 pounds of freon ?
    I think you mean 50 pounds of pressure on the high side, not 50 pounds of freon in the system. Never seen a system take even 1/4 of that amount.
    And probably not real freon.How about 134a refrigerant ?
     
    Opendeckin and leftlanetruckin Thank this.
  5. Ridgeline

    Ridgeline Road Train Member

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    I assume you have an '04 WS?

    IF so your body computer may be in control of the A/C.
     
    wore out Thanks this.
  6. snowwy

    snowwy Road Train Member

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    you seem smart enough to figure it out.

    but if you want, you can call it refrigerant, and i'll just stick with the shortened word freon. since we're both talking about the same thing.

    and since your on the subject. what IS real freon?

    as for systems. i hauled a chiller last week. supposedly takes 65 lbs.
     
    Cetane+ Thanks this.
  7. 04 LowMax

    04 LowMax Medium Load Member

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    You were absolutely right! I had not thought of that. Got it charged up and it's working well. Thank you! If anybody wants to pick apart your terms or wording, it's not me. I knew what you meant. Ridgeline you are probably right about the computer running it, but, for now anyway, it's working. Thanks.
     
    Cwalker and Cetane+ Thank this.
  8. snowwy

    snowwy Road Train Member

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    i wouldn't be jumping for joy just yet. if it was that low to not work. you might have a leak. keyword MIGHT.

    good to hear though.
     
  9. Bconnor92

    Bconnor92 Bobtail Member

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    Jun 30, 2017
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    I am not getting any power to my high or low switches or to my compressor and just replaced the ac pump still not getting any power or air
     
  10. Cetane+

    Cetane+ Road Train Member

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    So tell us what you have done to try to trouble shoot so far. What hvac system do you have, lever or digital? Have you checked the fuses, wires anything else? Year / model , did the a/c ever work before that you know of? Does the heat, fan/blower work? If you do have a blue a/c switch are you sure it works and is activating the a/c system? The switch does go bad.
     
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