Lennox G27M Series Unit Information

Page 23
VIII–SureLight Control Troubleshooting Guide
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 re-
set 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,
replace loose connectors.
ACTION 3 – Check continuity of switch in
closed position. Replace if defective.
1.1.5
Transformer Failure.
ACTION 1 – Check that transformer output is
24V. Replace if defective.
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.
co e
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.
LED
#1–
O
n,
LED#2–Slow Flash
1.2.3
Miswiring or improper connections
ACTION 1 – Check wiring connections to
Mi
sw
i
r
i
ng or
i
mproper connec
ti
ons
at roll–out switch.
g
switch.
1.2.4
Nine pin connector failure
ACTION 1 – Check 9–pin connector for prop-
er 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 ener
g
ize.
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 neu-
tral correctly input into control.
ACTION 2 – Reverse the line and neutral at the
120V field connection.
LED#1–Fast Flash,
LED#2–Slow Flash.
1.4
– On initial power up the combus-
tion 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.
pp
LED#1–Slow Flash
LED#2–Slow Flash
1.4.2
Failed combustion air blower motor.
ACTION 1 – If power is present at blower, re-
place blower.

Lennox G27M Series Specifications

General

Brand	Lennox
Model	G27M Series
Category	Furnace
Language	English