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  1. #27
    Join Date
    Nov 2004
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    up in the hizzy
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    1,291
    Quote Originally Posted by MattMP1 View Post
    the smoke detector should be breaking R, not just G

    if you been at it for some time, you probably would had see it configured in more than one way.
    I bet a six pack there a bad duct detector in that unit.

  2. #28
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,808
    Quote Originally Posted by valdelocc View Post
    if you been at it for some time, you probably would had see it configured in more than one way.
    I bet a six pack there a bad duct detector in that unit.
    Good possibility.
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  3. #29
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    17,020
    Quote Originally Posted by valdelocc View Post
    I think hes talking about a smoke detector, thats would kill the blower when tripped.
    (Maxwell Smart voice)

    "Ah, the old economizer smoke detector trick!"
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    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  4. #30
    Join Date
    Jan 2010
    Posts
    5,812
    Quote Originally Posted by valdelocc View Post
    nope mechanical cooling control interlocked with fan contractor, very simple stuff! sooner or later you'd run into one.
    Could you get a model number on one of these units ?
    I would like to pull up the wiring diagram.
    Thanks,
    VTP

  5. #31
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    17,020
    I've seen the need for a G signal on the older York units. I'm eager to find out which Carrier units need it, too.
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    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  6. #32
    Join Date
    Jan 2010
    Posts
    5,812

  7. #33
    Join Date
    Mar 2010
    Location
    Arnold, Mo
    Posts
    360
    Quote Originally Posted by valdelocc View Post
    I think hes talking about a smoke detector, thats would kill the blower when tripped.
    You are correct. I took it out and cleaned it up. It's a smoke detector. It was covered with about 1/4" of dust. So far it hasn't tripped again. Thanks to everyone for their help!

  8. #34
    Join Date
    Aug 2006
    Posts
    2,557
    We have RTUs with the board on the relay, the back side of the board the male push on terminal solder connection breaks. Sometimes just pulling the cover off will start / stop the fan. A little flux on the terminal, bit of solder on solder iron tip, and just touch the solder connection, as soon as it melts pull off. Do all of them as you can't see which one is broken. Don't forget to clean the flux off!!

  9. #35
    Join Date
    Mar 2010
    Location
    Arnold, Mo
    Posts
    360
    It ended being the in-duct smoke detector. It cuts out the blower when tripped. I will keep your advice in mind on the next time it happens. Thanks for the input.

  10. #36
    Join Date
    Apr 2010
    Location
    Upstate New York
    Posts
    31

    Thumbs up

    Consulting the schematic would have made troubleshooting this issue easier. No voltage at contactor coil... find the contactor coil on the schematic and check for voltage on each point you trace on the schematic all the way back to the contactor. There should be nothing mysterious about how a unit operates if a good schematic is available.

    When you work on larger equipment or unfamiliar equipment, a good schematic is priceless. You may have a huge control section full of components you don't recognize and over a hundred terminals. Without a schematic, diagnosing a problem as simple as a bad relay could take many hours. With a schematic, and you've got it figured out with 5-10 checks with your multimeter.

  11. #37
    Join Date
    Mar 2010
    Location
    Arnold, Mo
    Posts
    360
    The smoke detector wasn't on the schematic.

  12. #38
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    17,020
    Quote Originally Posted by flanders View Post
    The smoke detector wasn't on the schematic.
    Thats true. Very often, a smoke detector wont be on the schematic.

    However, if you start following the circuit ON the schematic, you will quickly find where you lose the power, which in this case is the smoke detector.
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    2 Tim 3:16-17

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  13. #39
    Join Date
    Jan 2010
    Posts
    5,812
    Had two out of three units down last week for the same reason. All three units wired together. Unit one was OK but unit two cutout number two and number three.

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