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Thread: McQuay AGS

  1. #1
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    McQuay AGS

    Got a AGS175 that we picked up a year or so ago. Had alot of control issues and what not......but got most of it resolved. One problem that kept creeping up.......slide valve sensor fault on circuit 1 and 2. Re calibrated sensors and all was good. But circuit 2 keeps locking out on the fault. It could be 1 week or 2 months. Reset it and everything looks good.

    So finally last month, I replaced the slide valve sensor and all the wiring. Everything look good and I left it. Today, I find it locked out again. And it was reading 28% off at 0%.

    So I again calibrated sensor. Ran it up and down for a hour and it's within 1%.

    What is causing this thing to go out of wack? I verified fully loaded and fully unload by signal to load/unload valves and amperages compared to 1st circuit. Everything is new. And normally, after reset the slide valve's track within 3%.

    What I don't understand either is I get a "Slide Valve Sensor Alram". Which according to the manual, means the slide valve sensor is either open or shorted. The "Slide Valve Position Fault", is when it's tracking is 25% off.

  2. #2
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    which compressor? frame 4 or 3200.

  3. #3
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    Quote Originally Posted by freonrick View Post
    which compressor? frame 4 or 3200.
    It's got (2) HS3220's.

  4. #4
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    Dec 2011
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    could be connection at slide indicator,was overtightend or tip of indicator worn,save time and replace the complete indicator.

  5. #5
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    Quote Originally Posted by steveoo View Post
    could be connection at slide indicator,was overtightend or tip of indicator worn,save time and replace the complete indicator.
    I replaced the entire indicator. The old one had a ball at the end. The new one had a plastic piece.

    I also replaced the cable from the terminal block to the sensor. I remove wiring from the terminal block to the Microtec II controller and restripped and landed them.

    I checked on the machine, yesterday. And both valves were within 1%. But in the past the machine has gone a month with no problems.

    Sent from my C771 using Tapatalk 2

  6. #6
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    I don't have any good advice, I just want to hear what ended up fixing it.

    The machines that we lost that had those compressors had one indicator short and blew up the input for its controller. Not very cool. That doesn't sound like what you're dealing with, thankfully.

  7. #7
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    Jan 2005
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    Houston TX
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    AGS Slide valve ind.

    ascj- I don't know if you have the code keys on hand but after all you gone through I would suggest downloading code just to be safe. You have done everything I would have done in this case. The one with the metal end was deleted from stock because they were wearing a groove in the slide valve bar that moves the sensor in and out as the slide loads and unloads. We have had several AGS's that needed to have code downloaded because of sensor error.=GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  8. #8
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    Dec 2011
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    what about the transducer coverter board on bottom of compresser controller,or is it a single controller?make sure converter board or transducers not causeing power dip,reference signal from slide is also connected to board.

  9. #9
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    Quote Originally Posted by ga1279 View Post
    ascj- I don't know if you have the code keys on hand but after all you gone through I would suggest downloading code just to be safe. You have done everything I would have done in this case. The one with the metal end was deleted from stock because they were wearing a groove in the slide valve bar that moves the sensor in and out as the slide loads and unloads. We have had several AGS's that needed to have code downloaded because of sensor error.=GEO
    Yeah......that might be my last resort. I know we have had numerous issues with RPS rtu's and having reload controllers.

  10. #10
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    Quote Originally Posted by steveoo View Post
    what about the transducer coverter board on bottom of compresser controller,or is it a single controller?make sure converter board or transducers not causeing power dip,reference signal from slide is also connected to board.
    There is no converter board. Circuit controller feed 21vdc to sensor. And a 4-20mA signal back. Voltage has always been good. I have tugged and messed with all the wiring while checking voltage.

    As far as the current readings. They have always been spot on to what the controller is showing (Slide valve position). For example......this last time I had to recalibrate- Circuit was calling for 0% at start-up. I had 8.49mA reading coming for sensor.

  11. #11
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    So no lock outs since my last post.

    Well I'm getting lock outs again. It seems to be related to outdoor temperature. I checked the oil heater and it's functioning.

    I finally caught it today. Compressor was calling to load up and slide valve position was sitting at 0%. Checked amperage of compressor and it was loading. I had to disconnect sensor to check current signal. Of course, I restarted with meter attached and all was well. Current signal and position showed good.

  12. #12
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    if the screw that holds the wiring plug to the indicator is over tightened it will damage the indicator. it does not take much. does this indicator have a round cap that removes and has a led light with push button inside? if so removing electrical plug while running will ruin the indicator.

  13. #13
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    I replaced the entire assembly, wiring harness, and plug 3 months ago. Don't think I over tighten it. To take my current reading from the sensor......I pump down circuit, pull 21vdc plug from Mircotech II, and then remove sensor reading wiring and splice in my meter.

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