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  1. #1

    Carrier 40QNB024 Split Not sending signal

    We have a carrier 40QNB024 High Wall Fan Coil Unit, that has decided to not tell the outside unit to come on.

    The manual states that there is diagnostic LED codes to help you to troubleshoot, but the system doesn't think there is an error.

    We've
    - reset the unit completely (remote too)
    - Bypassed the drain pump to ensure it wasnt a pump failure
    - put new batteries into the remote..

    the outside just doesn't get the signal when its operating in normal mode.
    If i throw it to 'test' then it cools down fast, but if I set it to its normal day to day, it could work for a couple hours, then stop working (and again, no LED's blinking to signal an error). After going over it, my carrier dealer has determined that he thinks its the controller board ( 42KNAB850LF or 42KNAB5850LF). But Carrier (Canada) doesn't have the board, and carrier US says they aren't running production until Mid October.. and maybe 4 weeks after that they would have special order stock to send me one.

    So.. I'm looking for someone that either may have one, or if anyone has any other thoughts. we're scratching our heads over it.

    Thanks

  2. #2
    Join Date
    Aug 2008
    Posts
    91

    Wink

    Experienced a problem similar to this with Teledyne. The problem would clear up when the system was put into debug and after it was placed back in normal mode it would re-appear. It ended up being an instruction block of code and as with your problem it would never show a fault. What was really strange is that the block of code wasn't even being used just the controller block was there for if this block of code was needed.

    So maybe this will help out when viewing the instruction block. It's also possible that it could be a communication problem when the controller's talk to each other.

  3. #3
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,278
    After you set it, try taking the batteries out of the remote and placing a piece of tape over the communication window.

    Sounds crazy, but I have seen this work on more then one occasion.

  4. #4
    Join Date
    Aug 2008
    Posts
    91

    Unhappy

    Quote Originally Posted by Hardwater View Post
    Experienced a problem similar to this with Tridium. The problem would clear up when the system was put into debug and after it was placed back in normal mode it would re-appear. It ended up being an instruction block of code and as with your problem it would never show a fault. What was really strange is that the block of code wasn't even being used just the controller block was there for if this block of code was needed.

    So maybe this will help out when viewing the instruction block. It's also possible that it could be a communication problem when the controller's talk to each other.
    Put wrong controls down its Tridium. Sorry!

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