Lennox G26Q3/4-100 User Manual

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Page 43
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 combustion
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 improper
main ground.
1.5.2
6-Pin connector is improperly atĆ
tached to the circuit board.
ACTION 1 - Check 6-pin connector for proper
installation. Correctly insert connector into conĆ
trol.
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 supĆ
ply correct voltage to the control.
PROBLEM 2: UNIT FAILS TO OPERATE IN THE COOLING OR HEATING MODE, BUT COMBUSĆ
TION AIR BLOWER OPERATES CONTINUOUS. UNITS WITH CONTROL BOARDS DATE CODED
AFTER NOV.1 1997, WILL OPERATE IN COOLING BUT NOT IN THE HEATING MODE, WITH COMĆ
BUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF.
Condition Possible Cause Corrective Action / Comments
2.1
- On initial power-up the combustion
air blower remains energized.
- Diagnostic lights flash the improper
main ground.
- Units with control boards date
coded after Nov 1 1997; combustion
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 installation.
coded after Nov.1 1997; combustion
air blower will cycle 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 resistance
across ignitor. If resistance does not read beĆ
tween 10.9 and 19.7 ohms, replace the 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 conĆ
tinuous fan demand.
- Combustion air blower will not start
with a Heating demand.
- Diagnostic lights flash the limit failure
d
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. Determine
cause for limit activation before placing unit back
in operation.
gg
mode.
LED#1-Slow Flash,
LED#2-On
3.1.2
Miswiring of furnace or improper conĆ
nections at limit switch(es).
ACTION 1 - Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
3.2
- Unit operates with a cooling and conĆ
tinuous fan demand.
- Combustion air blower will not start
with a Heating demand.
- Dia
g
nostic li
g
hts flash the
p
ressure
3.2.1
Miswiring of furnace or improper conĆ
nections to combustion air blower.
ACTION 1 - Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
-
Diagnostic
lights
flash
the
pressure
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 operatĆ
ing. Replace if malfunctioning

Lennox G26Q3/4-100 Specifications

General

Brand	Lennox
Model	G26Q3/4-100
Category	Furnace
Language	English