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  1. #1
    Join Date
    Dec 2011
    Location
    Twin Cities Minnesota
    Posts
    239

    BLOWER WONT STOP

    Rudd JGDG075AUER serCB5D302F38951719 After A/C hits its set point,Cond. shuts down blower keeps going. Remove 24v at board feeding stat,not that. Pull blower wire at "cool",nope! pulled blower wire at "heat" bingo! Got to thinking..,are hi limits etc. active in A/C call? in this unit they are. I had 24v.at all safty switches. They all tested Ok. BAD BOARD was my first and still diagnoses. Records show this is the 3rd board in as many years! I also checked voltage of unused blower wires while running in A/c mode.One to the heat spade was 115v,other 2 on park pins were 160v! ( is this normal,or do I have a blower that needs an exorcism?

  2. #2
    Join Date
    Jun 2013
    Location
    Northeast Wi
    Posts
    167
    Are the replacement boards aftermarket or oem? I had the same issue with an oem board and replaced it with a honeywell s920u. The honenywell has jumper wires and dip switch that need to set. What about polarity? Sounds like a stuck relay.

  3. #3
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,033
    Quote Originally Posted by Cosmicmuffin View Post
    Rudd JGDG075AUER serCB5D302F38951719 After A/C hits its set point,Cond. shuts down blower keeps going. Remove 24v at board feeding stat,not that. Pull blower wire at "cool",nope! pulled blower wire at "heat" bingo! Got to thinking..,are hi limits etc. active in A/C call? in this unit they are. I had 24v.at all safty switches. They all tested Ok. BAD BOARD was my first and still diagnoses. Records show this is the 3rd board in as many years! I also checked voltage of unused blower wires while running in A/c mode.One to the heat spade was 115v,other 2 on park pins were 160v! ( is this normal,or do I have a blower that needs an exorcism?
    That higher voltage on park terminals is due to the back EMF it is normal. The series safety circuit can be energized at all times, I have seen this with janitrols. Is their more than one safety circuit? Sometimes the liimit switch that sets beside the heat exchanger has its own circuit. It could be open that would keep the fan on constantly.

  4. #4
    Join Date
    Dec 2011
    Location
    Twin Cities Minnesota
    Posts
    239
    Its a Honeywell 47-22827-03 board. All safety switches i could find were N/O. I made a second trip back,to verify before ordering board!

  5. #5
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,967
    Quote Originally Posted by Cosmicmuffin View Post
    Rudd JGDG075AUER serCB5D302F38951719 After A/C hits its set point,Cond. shuts down blower keeps going. Remove 24v at board feeding stat,not that. Pull blower wire at "cool",nope! pulled blower wire at "heat" bingo! Got to thinking..,are hi limits etc. active in A/C call? in this unit they are. I had 24v.at all safty switches. They all tested Ok. BAD BOARD was my first and still diagnoses. Records show this is the 3rd board in as many years! I also checked voltage of unused blower wires while running in A/c mode.One to the heat spade was 115v,other 2 on park pins were 160v! ( is this normal,or do I have a blower that needs an exorcism?
    Probably a stuck relay on the board, if you install another board, make sure since this is the 3rd board, some "blow and go" tech did not install the wrong hp motor were it's drawing to many amps for the relay on that board, seen this before.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  6. #6
    Join Date
    Jun 2013
    Location
    Northeast Wi
    Posts
    167
    Any signs of water?

  7. #7
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,033

    BLOWER WONT STOP

    Quote Originally Posted by Cosmicmuffin View Post
    Its a Honeywell 47-22827-03 board. All safety switches i could find were N/O. I made a second trip back,to verify before ordering board!
    Only N/O safety switch im aware of is a pressure switch for inducer motor?

  8. #8
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,344
    Quote Originally Posted by Core_d View Post
    Only N/O safety switch im aware of is a pressure switch for inducer motor?
    Yep. I'd listen to Mr. Bill, especially if the previous boards were replaced for the same reason.

    How likely is it a limit would open and stick open during AC season?

  9. #9
    Join Date
    Dec 2011
    Location
    Twin Cities Minnesota
    Posts
    239
    Opps they were N.C. switches (good eye). Yes there is some moisture issues,very wet basement!

  10. #10
    Join Date
    Feb 2011
    Location
    North East Ohio
    Posts
    772
    Any fault codes? Not familiar with this model but is there a discharge air sensor?

  11. #11
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,222
    Do you hear the fan relay click when the power to the furnace is first energized?
    Another test you can do is take where the power comes into the board and ohm it to the motor output terminal that is staying energized. If it reads shorted the contacts are arced.

  12. #12
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,033
    Quote Originally Posted by hurtinhvac View Post

    How likely is it a limit would open and stick open during AC season?
    True, and for that matter Im sure if cooling would come on with an open limit. Ive been told the blower staying on is to alert the home owner of a problem.

  13. #13
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,222
    Quote Originally Posted by Core_d View Post
    True, and for that matter Im sure if cooling would come on with an open limit. Ive been told the blower staying on is to alert the home owner of a problem.
    Newer systems are cutting the 24V to the thermostat when they hit high limit:
    http://hvac-talk.com/vbb/showthread....1#post14887221

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