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Thread: 48HG Economizer Motor going to 100%

  1. #1
    Join Date
    Apr 2008
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    48HG Economizer Motor going to 100%

    48HGE024AB-72048. The economizer motor will go to 100% intermittently, but currently is all the time and stays there, even after powering the unit off and back on. It's not the IAQ. System is not switched to Cooling, so not the Economizer per se. I have 4 VAC on TB5 terminals 8+9 and 10 VDC on 9+10 at 100% open position. When I jumper 8 to 10, motor drives closed and voltages are -2 VDC on 8+9 and 2 VDC on 9+10. Makes it difficult to heat the place using 35 degree outside air. When I left there about a week ago, the motor was acting properly.
    Terminal 8 is the VDC in to the motor (3), 9 is motor common (1) , and 10 is VDC out from motor (5).
    Some time ago, the display read 0% position of the motor when it was at 100%.
    Currently have the ECON option disabled.
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  2. #2
    Join Date
    Jul 2005
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    Have you looked at configuration tables for proper configuration?
    Have you tried to operate economizer in test mode?
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  3. #3
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    Apr 2008
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    Thread Starter
    I was hoping for someone that had this same problem. I have checked the configurations. Unit has been running for 20 or so years. This showed up about a year ago, off and on. IAQ is not enabled and I guess it never has been. IAQ was my first suspicion.

  4. #4
    Join Date
    Nov 2011
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    CO
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    Not familiar with that particular unit, but I would verify all sensors and transducers are reading correctly, and all match resistance/ voltage charts.

    Also check every single wire connection, plug, terminal block, etc. Tighten all screws, pull on wires, tug on connectors, inspect all connector pins.

    I have also ohm'd wires between components to verify they had no breaks.

    After that, you're left with component problems. Then you can test board outputs, and try to nail down which component is flaking out.

    Or you may find that, after you go through all the wiring, the problem mysteriously disappears. A loose connection would explain the unexplained intermittent activity.

  5. #5
    Join Date
    Apr 2008
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    Thread Starter
    I did remove and replace all the plugs on the circuit boards. There is a thermistor for the 3rd stage compressor that gave an error code and the resistance was only 151, but it fixed itself for a week or so, but I ordered a new one because I knew it wasn't actually fixed. Now it is acting up again and I have the new one ready. They should not have anything to do with each other, but I will replace the thermistor and see what happens.

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