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  1. #1
    Join Date
    Mar 2020
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    Limit Switch Open Error ICP Furance

    Have a customer with a ICP high efficiency furnace, throwing a 4 flashing light code, limit switch open. Here is what I have done so far (most as part of general service):
    Changed 2 x limit switch
    Changed Pressure switch
    Changed ignitor
    Changed flame sensor
    Changed board

    Anyone any ideas with these furnaces as to why it would still throw this code after this?

  2. #2
    Join Date
    Sep 2002
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    Virginia
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    Have you made sure polarity is correct , you know , the switch on blower door is hot ( not neutral) and the ground is nice and snug

  3. #3
    Join Date
    Oct 2014
    Location
    Saint Pail, Minnesota
    Posts
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    Is the limit actually open?
    Did you replace all those things in response to this one error code?
    Are you a technician? If you are you need to contact a more senior tech to show you how to trouble shoot properly. You have replaced everything but motors and heat exchanger, customer would have been better off with a sales tech in this case.

  4. #4
    Join Date
    Mar 2020
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    Thread Starter
    The main fan comes
    On when the switch is activated but that is as far as the cycle goes

  5. #5
    Join Date
    Sep 2002
    Location
    Virginia
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    Do you know how to test across a safety switch to see if its open or closed ?

    You know its got a couple different high limits ... right

    Some have 3 - 4 of them

  6. #6
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    Call A professional

  7. #7
    Join Date
    Mar 2016
    Location
    Dayton Oh
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    2,339
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    Limit switch or pressure switch?

    If limit switch why replace a pressure switch?
    Or vise versa?

    Like others said, is the limit actually open? Ohm meter the limits and see if they are open and close.

    After the furnace is off for an hour does the furnace run at all or go right to error code?

    Which limit, roll out or HX high limit?


    Sent from my iPhone using Tapatalk

  8. Likes jmac00 liked this post.
  9. #8
    Join Date
    Jul 2007
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    Virginia
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    Quote Originally Posted by The Gaffer View Post
    Have a customer with a ICP high efficiency furnace, throwing a 4 flashing light code, limit switch open.
    Model number please.
    Instead of learning the tricks of the trade, learn the trade.

  10. #9
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    16,479
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    some furnaces have a limit switch on the blower housing, which MANY techs miss.

    someone needs to figure out how to test a safety circuit, instead of loading up the parts cannon
    PANIC
    Rarely works

  11. #10
    Join Date
    Oct 2011
    Location
    Culver, Oregon (Central OR)
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    Quote Originally Posted by jmac00 View Post
    some furnaces have a limit switch on the blower housing, which MANY techs miss.

    someone needs to figure out how to test a safety circuit, instead of loading up the parts cannon
    Bingo!! These get missed all the time. Betcha that's what it is.

  12. #11
    Join Date
    Mar 2016
    Location
    Dayton Oh
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    Quote Originally Posted by jmac00 View Post
    some furnaces have a limit switch on the blower housing, which MANY techs miss.

    someone needs to figure out how to test a safety circuit, instead of loading up the parts cannon
    Do icp have those? I know that’s a big trane thing.


    Sent from my iPhone using Tapatalk

  13. #12
    Join Date
    Aug 2008
    Location
    Hibbing, MN
    Posts
    821
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    He forgot to change the inducer motor and heat exchanger. I hate when people only replace MOST of the parts. Do the job right, and replace them all. Darn Millennials!
    If God didn't want us to eat animals... He wouldn't have made them out of MEAT.

  14. Likes doc havoc liked this post.
  15. #13
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
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    Quote Originally Posted by The Gaffer View Post
    Have a customer with a ICP high efficiency furnace, throwing a 4 flashing light code, limit switch open. Here is what I have done so far (most as part of general service):
    Changed 2 x limit switch
    Changed Pressure switch
    Changed ignitor
    Changed flame sensor
    Changed board

    Anyone any ideas with these furnaces as to why it would still throw this code after this?
    Wow! That’s getting expensive. Evidently none of those parts were bad. Tell us what you measured instead of what you guessed at.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

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