Lennox G27M

[dhowell]

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?

[t527ed]

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...........:(

[40_cents]

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. :)

[AtticAce]

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.