Control Signals Low Flame Sense During Heating Mode; Indoor Blower Fails To Operate In Cooling, Heating, Or Continuous Fan Mode - Lennox G60UHV Service Manual

PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
6.5
− Combustion air inducer energizes
with a heating demand.
− Burners light.
− Diagnostic lights flash watch guard
flame failure.
− NOTE" Unit might go into 60 minute
Watchguard mode depending on in-
termittent nature of sensor signal.
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE
Condition
7.0
− Unit operates correctly but the diag-
nostic lights flash low flame sense
code.
LED#1−Slow Flash
LED#2−Fast Flash
PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS
Condition
8.0
− Indoor blower fails to operate in
continuous fan, cooling, or heating
mode.
PREMATURELY (CONT.)
6.5.1
Loose sensor wire connection causes
intermittent loss of flame signal.
6.5.2
Poor ground to burner box
Possible Cause
7.1.1
Sense rod is improperly located on
the burner.
7.1.2
Sense rod is contaminated.
FAN MODE
Possible Cause
8.1.1
Miswiring of furnace or improper con-
nections at control or indoor blower
motor.
8.1.2
120V is not being supplied to the in-
door air blower or blower motor fail-
ure.
8.1.3
Defective control board
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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.
ACTION 1 − Check for proper ground and repair
as necessary.
Corrective Action/Comments
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.
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.
Corrective Action/Comments
ACTION 1− Correct wiring and/or replace any
loose connections. Check for correct wiring and
loose connections.
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.
ACTION 1 − If there is not 120V when "Y", "G", or
"W" is energized, replace the control.