Lennox G60UH - Troubleshooting Flame Sense and Blower Failures

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PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY (CONT.)
6.5
− Combustion air inducer energizes
with a heating demand.
− Burners light.
− Dia
g
nostic li
g
hts flash watch
g
uard
6.5.1
Loose sensor wire connection causes
intermittent loss of flame signal.
ACTION 1 − Check that the sensor is properly lo-
cated.
ACTION 2 − Check that the sense wire is properly
attached to both the sensor and the control. Pay
extra attention to the pin connectors.
−
Diagnostic
lights
flash
watch
guard
flame failure.
− NOTE" Unit might go into 60 minute
Watchguard mode depending on in-
termittent nature of sensor signal
6.5.2
Poor ground to burner box
ACTION 1 − Check for proper ground and repair
as necessary.
t
erm
itt
en
t
na
t
ure o
f
sensor s
i
gna
l
.
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
6.5.3
Prove Switch opens 5 times during a
single demand
ACTION 1 − Inspect vent pipe installation and for
any restriction. Remove restriction.
ACTION 2 − Check prove switch reliability.
PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE
Condition Possible Cause Corrective Action/Comments
7.0
− Unit operates correctly but the diag-
nostic lights flash low flame sense
code
7.1.1
Sense rod is improperly located on
the burner.
ACTION 1 − Check the sense rod for proper loca-
tion on the burner. Properly locate the sense rod
or replace if rod cannot be located correctly.
code
.
LED#1−Slow Flash
LED#2−Fast Flash
7.1.2
Sense rod is contaminated.
ACTION 1 − Check sense rod for contamination
or coated surface. Clean the sense rod with steel
wool or replace sensor. DO NOT USE SAND PA-
PER TO CLEAN ROD. SAND PAPER WILL
CONTRIBUTE TO THE CONTAMINATION
PROBLEM.
PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS
FAN MODE
Condition Possible Cause Corrective Action/Comments
8.0
− Indoor blower fails to operate in
continuous fan, cooling, or heating
mode.
8.1.1
Miswiring of furnace or improper con-
nections at control or indoor blower
motor.
ACTION 1− Correct wiring and/or replace any
loose connections. Check for correct wiring and
loose connections.
8.1.2
120V is not being supplied to the in-
door air blower or blower motor fail-
ure.
ACTION 1 − Check for 120V at the various calls
for indoor blower by energizing "Y", "G", and "W"
individually on the low voltage terminal strip. Note
that when "W’ is energized, the blower is delayed
45 seconds. If there is 120V to each motor tap but
the blower does not operate, replace the motor.
8.1.3
Defective control board
ACTION 1 − If there is not 120V when "Y", "G", or
"W" is energized, replace the control.
8.1.4
Defective run capacitor
ACTION 1 − Replace capacitor