Lennox G60UH - Troubleshooting Flame Sense and Blower Failures (Board 100869)

Page 62
PROBLEM 7: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY (CONT.)
Flash Code
LED X + Y
Possible Cause Corrective Action/Comments
7.5
Combustion air inducer energizes
with a heating demand.
− Burners light.
Diagnostic lights flash watch guard
flame failure.
NOTE
"
Unit might go into 60 minute
7.5.1
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.
NOTE
Unit
might
go
into
60
minute
Watchguard mode depending on
intermittent nature of sensor signal.
LED 4 + 3
7.5.2
Poor ground to burner box
ACTION 1 − Check for proper ground and repair
as necessary.
PROBLEM 8: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE
Condition Possible Cause Corrective Action/Comments
8.0
Unit operates correctly but the
diagnostic lights flash low flame
d
8.1.1
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.
sense code.
LED 1 + 2
8.1.2
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 9: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS
FAN MODE
Condition Possible Cause Corrective Action/Comments
9.0
− Indoor blower fails to operate in
continuous fan, cooling, or heating
mode.
9.1.1
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.
9.1.2
120V is not being supplied to the in-
door air blower or blower motor fail-
ure.
ACTION 1 − PSC MOTORS 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 oper-
ate, replace the motor.
ACTION 1 − VARIABLE SPEED MOTORS for
operation of the VSM see NO TAG
9.1.3
Defective control board
ACTION 1 − PSC MOTORS If there is not 120V
when "Y", "G", or "W" is energized, replace the
control.