Lennox G61MPV Service Manual page 107

PROBLEM 7: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
Flash Code
LED X + Y
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
Watchguard mode depending on
intermittent nature of sensor signal.
LED 4 + 3
PROBLEM 8: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE
Condition
8.0
Unit operates correctly but the
diagnostic lights flash low flame
sense code.
LED 1 + 2
PROBLEM 9: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS
Condition
9.0
− Indoor blower fails to operate in
continuous fan, cooling, or heating
mode.
PREMATURELY (CONT.)
Possible Cause
7.5.1
Loose sensor wire connection causes
intermittent loss of flame signal.
7.5.2
Poor ground to burner box
Possible Cause
8.1.1
Sense rod is improperly located on
the burner.
8.1.2
Sense rod is contaminated.
FAN MODE
Possible Cause
9.1.1
Miswiring of furnace or improper con-
nections at control or indoor blower
motor.
9.1.2
120V is not being supplied to the in-
door air blower or blower motor fail-
ure.
9.1.3
Defective control board
Page 107
Corrective Action/Comments
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 − 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 Page 41
ACTION 1 − PSC MOTORS If there is not 120V
when "Y", "G", or "W" is energized, replace the
control.