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  1. #1
    Join Date
    Mar 2005
    Posts
    10
    Any ideas? (Trane XE90, Model TUC080C942A0, Manu 1994)

    Pressure switch works, meaning it is open when the induction fan blows and is closed when it is not. With heat on each terminal reads ~26 volts.

    There is a sensor of some type on the inducer fan housing; it runs inline with the inducer motor. I tried bypassing this sensor and it made no difference.

    The furnace will produce heat/cycle on and off. The inducer motor however never wants to turn off.

    Thanks,

    Jason

  2. #2
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    It sounds like the contacts in control board are stuck if the t-stat is not calling for heat.

  3. #3
    does the blower also run or just inducer. & is the inducer control by the board is 120 volts from board at all times without call for heat.The presure switch should be closed when inducer is runinng unless on positive side of inducer.

  4. #4
    Join Date
    Mar 2005
    Posts
    24
    Originally posted by jasonv1
    Any ideas? (Trane XE90, Model TUC080C942A0, Manu 1994)

    Pressure switch works, meaning it is open when the induction fan blows and is closed when it is not. With heat on each terminal reads ~26 volts....
    You say the terminal reads 26v... I'm assuming you mean R & W terminals for Stat. What is the voltage off the motor? Unplug it and take a reading across the hot and common while calling for heat. Plug it back in and take an amp draw also. Relay may be bad on the board, there may be a line wire missplaced, etc. Give us a little more info please.

  5. #5
    Join Date
    Mar 2005
    Posts
    10
    Blower motor runs when it is supposed to (when burners are lit/for some time thereafter).

    Inducer motor is getting 120V from the control board.

    The pressure switch is closed (meaning current can pass) when the inducer is on.



    Originally posted by hot wired
    does the blower also run or just inducer. & is the inducer control by the board is 120 volts from board at all times without call for heat.The presure switch should be closed when inducer is runinng unless on positive side of inducer.

  6. #6
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    replace control board

  7. #7
    Join Date
    Mar 2005
    Posts
    10
    The thermostat does call for heat.

    When it stops calling for heat the inducer keeps running.

    Originally posted by jasonv1
    Any ideas? (Trane XE90, Model TUC080C942A0, Manu 1994)

    Pressure switch works, meaning it is open when the induction fan blows and is closed when it is not. With heat on each terminal reads ~26 volts.

    There is a sensor of some type on the inducer fan housing; it runs inline with the inducer motor. I tried bypassing this sensor and it made no difference.

    The furnace will produce heat/cycle on and off. The inducer motor however never wants to turn off.

    Thanks,

    Jason

  8. #8
    Join Date
    Mar 2005
    Posts
    10
    I was talking about the terminals on the pressure switch.

    Inducer motor reads ~120V. I didn't get an amp read yet.

    I'm leaning towards the board (stuck relay). Everything else on the thing works fine with the exception of the inducer motor just choosing to never turn off.



    Originally posted by kc_srvs
    You say the terminal reads 26v... I'm assuming you mean R & W terminals for Stat. What is the voltage off the motor? Unplug it and take a reading across the hot and common while calling for heat. Plug it back in and take an amp draw also. Relay may be bad on the board, there may be a line wire missplaced, etc. Give us a little more info please. [/B]

  9. #9
    Join Date
    Mar 2005
    Posts
    10
    That what I figured.

    A stuck realy seemed like the likely culprit.


    Originally posted by pipefitter2005
    replace control board

  10. #10
    Join Date
    Mar 2005
    Posts
    24
    I would definately replace the board then. If voltages are good and your not getting any fault codes stating there is a problem then it comes down to the board sending 120v to the inducer. No doubt in my mind that when you replace the board your problem will cease.

  11. #11
    Join Date
    Mar 2005
    Posts
    10
    Thanks.


    Originally posted by kc_srvs
    I would definately replace the board then. If voltages are good and your not getting any fault codes stating there is a problem then it comes down to the board sending 120v to the inducer. No doubt in my mind that when you replace the board your problem will cease.

  12. #12
    Join Date
    Mar 2005
    Posts
    24

    Thumbs up

    Any time pal!

  13. #13
    Join Date
    Mar 2005
    Posts
    10
    It was the board.

    Replaced it earlier today and the unit has been running for 90 minutes already with no problems. (It is bringing the house from 61 to 70 so it will take awhile).

    Thanks for the help!

    Jason

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