Lennox G24M SERIES Unit Information

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PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE
Condition Possible Cause Corrective Action / Comments
1.5
-- On initial power--up the combus-
tion air blower remains energized.
Di ti li ht fl h th i
1.5.1
Improper ground to the unit.
ACTION 1 --
Check that the unit is properly
ground.
ACTION 2 --
Install a proper main ground to
the unit
g
-- Diagnostic lights flash the im-
proper main ground.
1.5.2
6--Pin connector is improperly at-
tached to the circuit board.
ACTION 1 --
Check 6--pin connector for proper
installation. Correctly insert connector into
control.
LED#1--Alternating Fast Flash
LED#2--Alternating Fast Flash
1.5.3
Line voltage is below 75V.
ACTION 1 --
Check that the line voltage is
above 75V. Determine cause of voltage drop
and supply correct voltage to the control.
PROBLEM 2: UNIT OPERATES IN COOLING MODE BUT NOT IN THE HEATING MODE, WITH
COMBUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF.
Condition Possible Cause Corrective Action / Comments
2.1
-- On initial power--up the combus-
tion air blower remains energized.
-- Diagnostic lights flash the im
proper main ground.
Combustion air blower cycles 5
2.1.1
Open ignitor circuit.
ACTION 1 --
Check for correct wiring and
loose connections in the ignitor circuit. Check
mult--plug connections for correct installa-
tion.
--
C
om
b
ust
i
on a
i
r
bl
ower cyc
l
es 5
seconds on 55 seconds off.
LED#1--Alternating Fast Flash
LED#2--Alternating Fast Flash
2.1.2
Broken or failed ignitor.
ACTION 1 --
Unplug ignitor and read resis-
tance across ignitor. If resistance does not
read between 10.9and 19.7ohms, replacethe
ignitor.
PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES
NOT ENERGIZE
Condition Possible Cause Corrective Action / Comments
3.1
-- Unit operates with a cooling or
continuous fan demand.
-- Combustion air blower will not
start with a Heating demand.
-- Diagnostic lights flash the limit
failure mode
3.1.1
Primary or secondary (if equipped)
limit open.
ACTION 1 --
Check continuity across
switch(es). Switches reset automatically
upon cool down.
ACTION 2 --
Check for restrictions on blower
inlet air (including filter) and outlet air. Deter-
mine cause for limit activation before placing
unit back in operation.
f
a
il
ure mo
d
e.
LED#1--Slow Flash,
LED#2--On
3.1.2
Miswiring of furnace or improper
connections at limit switch(es).
ACTION 1 --
Check for correct wiring and
loose connections. Correct wiring and/or re-
place any loose connections.
3.2
-- Unit operates with a cooling and
continuous fan demand.
-- Combustion air blower will not
start with a Heating demand.
-- Diagnostic lights flash the pres-
sure switch failure code
3.2.1
Miswiring of furnace or improper
connections to combustion air
blower.
ACTION 1 --
Check for correct wiring and
loose connections. Correct wiring and/or re-
place any loose connections.
sure switch failure code.
LED#1--Off,
LED#2--Slow Flash
3.2.2
Pressure switch stuck closed.
ACTION 1 --
Check that the pressure switch is
open without the combustion air blower op-
erating. Replace if malfunctioning

Lennox G24M SERIES Specifications

General

Brand	Lennox
Model	G24M SERIES
Category	Furnace
Language	English