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Thread: Lennox G27M

  1. #1
    Join Date
    Nov 2007
    Location
    SE Michigan
    Posts
    1

    Lennox G27M

    I woke up this morning to no heat.
    I have a lennox g27m no system lights are on.
    What would be my initial troubleshooting step?

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,736
    if no lights are on make sure power did not get turned off.

    if power is on call for service, it won't be an easy fix...........

  3. #3
    Join Date
    Aug 2006
    Location
    Seattle Area
    Posts
    38

    No Lights.. No Power?

    Had this happen to a customer once.. I get called out in the AM on Saturday for a emergency no heat call... I get there and check the T-Stat and it shows a call for heat. I walk down to the basement with the owner and notice the power switch was off along with some kind of stuffed mouse near the filter door in the drop... I laughed and asked if there was a stuffed mouse problem in the area. I turned the switch on and the furnace fired up. The owner remembered that his cat loves playing near the furnace. Best we can deduct (other than a haunting) the cat must have switched the furnace off. Please.... I Beg of you.... Check your power switch, and Breaker before calling.. It will save you some money.

  4. #4
    Join Date
    Jul 2007
    Location
    Beautiful, Philadelphia, the City of Brotherly Love!
    Posts
    1,096

    This is from the service manual that is in your paper work.

    VIII− Troubleshooting Guide SureLight Control
    UPON INITIAL POWER UP, REMOVE ALL THERMOSTAT DEMANDS TO THE UNIT
    PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE
    Condition Possible Cause Corrective Action / Comments
    1.1
    − Both diagnostic lights fail to light up.
    1.1.1
    Main voltage 120V not supplied to
    unit.
    ACTION 1 − Check 120V main voltage.
    Determine cause of main power failure.
    LED#1−Off
    LED#2−Off
    1.1.2
    Miswiring of furnace or improper
    connections.
    ACTION 1 − Check for correct wiring of 120V to
    power make up box and transformer.
    ACTION 2 − Check 24V wiring to control board.
    1.1.3
    Circuit breaker tripped or fails to
    close.
    ACTION 1 − Replace circuit breaker if it is reset
    but does not have continuity.
    ACTION 2 − If circuit breaker still trips, check for
    short.
    1.1.4
    Door interlock switch failure.
    ACTION 1 − Check that door switch is activated
    when door is closed.
    ACTION 2 − Check wire connections to switch, re
    place loose connectors.
    ACTION 3 − Check continuity of switch in closed
    position. Replace if malfunctioning
    1.1.5
    Transformer Failure.
    ACTION 1 − Check that transformer output is
    24V. Replace if malfunctioning
    1.1.6
    Failed control board.
    ACTION 1 − If all the above items have been
    checked, replace board.
    1.2
    − Diagnostic lights flash the roll−out
    code.
    1.2.1
    Roll−out switch open.
    ACTION 1 − Manually reset the roll−out switch
    by pushing the top button.
    ACTION 2 − Determine the cause of the roll−out
    switch activation before leaving furnace. LED#1 O
    1.2.2
    Roll−out switch failure.
    ACTION 1 − Check continuity across roll−out
    switch. Replace roll−out switch if switch is reset
    but does not have continuity.
    1−On,
    LED#2−Slow Flash
    1.2.3
    Mis iring or improper connections at
    ACTION 1 − Check wiring connections to switch 2 Miswiring roll−out switch.
    switch.
    1.2.4
    Nine pin connector failure
    ACTION 1 − Check 9−pin connector for proper
    connection to control board.
    ACTION 2 − Check continuity of the multi plug
    pin.
    1.3
    − On initial power−up the comb. air
    blower does not energize.
    − Diagnostic lights flash the reverse
    polarity code.
    1.3.1
    120V main power polarity reversed.
    ACTION 1 − Check the 120V has line and neutral
    correctly input into control.
    ACTION 2 − Reverse the line and neutral at the
    LED#1−Fast Flash,
    LED#2−Slow Flash.
    120V field connection.
    1.4
    − On initial power up the combustion
    air blower does not energize.
    − Diagnostic lights flash normal power
    on operation.
    1.4.1
    Open combustion air blower motor
    circuit.
    ACTION 1 − Check for 120V to combustion air
    blower. If no power, check wire and connec
    tions.
    LED#1−Slow Flash
    LED#2−Slow Flash
    1.4.2
    Failed combustion air blower motor.
    ACTION 1 − If power is present at blower, replace
    blower.

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