Whirlpool WFM18 Installation Instructions Manual page 33

80% single-stage multispeed gas furnace
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Problem
Furnace fails to operate
Integrated control module
diagnostic LED provides
no signal
LED is steady On.
Furnace fails to operate.
Integrated control module
diagnostic LED is flashing
1 flash.
Furnace fails to operate.
Integrated control module
diagnostic LED is flashing
2 flashes.
Induced draft blower runs
continuously with no
further furnace operation.
Integrated control module
diagnostic LED is flashing
3 flashes.
Circulator blower runs
continuously. No furnace
operation.
Integrated control module
diagnostic LED is flashing
4 flashes.
LED Code
Fault/Cause
None
No 115-volt power to furnace, or no
24-volt power to integrated control
module.
Blown fuse or circuit breaker.
Internal fault in Integrated control
module.
Manual disconnect switch off, door
switch open or 24-volt wires
improperly connected or loose.
Continuous
Normal
On—not
flashing
1 flash
Furnace lockout due to an excessive
number of ignition "retries" (3 total).
Auxiliary limit switch open.
Failure to establish flame. Cause may
be no gas to burners, bad igniter or
igniter alignment, improper orifices or
coated/oxidized or improperly
connected flame sensor.
Loss of flame after establishment.
Cause may be interrupted gas supply,
lazy burner flames (improper gas
pressure or restriction in flue) or
improper induced draft blower
performance.
Insufficient conditioned air over the
heat exchanger. Blocked filters,
restrictive ductwork, improper
circulator blower speed or failed
circulator blower.
2 flashes
Pressure switch circuit is closed.
Induced draft blower is not operating.
Induced draft blower pressure switch
contacts sticking.
Shorts in pressure switch circuit.
3 flashes
Pressure switch circuit not closed.
Induced draft blower is operating.
Pressure switch hose blocked, pinched
or connected improperly.
Blocked flue or weak induced draft
blower.
Incorrect pressure switch setpoint or
malfunctioning switch contacts.
Loose or improperly connected wiring.
4 flashes
Primary limit circuit is open.
Insufficient conditioned air over the
heat exchanger. Blocked filters,
restrictive ductwork, improper
circulator blower speed or failed
circulator blower.
Faulty primary limit switch.
Loose or improperly connected wiring.
Solution
Verify that there is 115-volt power to the
furnace and 24-volt power to integrated
control module
Replace fuse or circuit breaker.
Check integrated control module fuse
(3A). Replace if necessary.
Check for possible shorts in 115- and
24-volt circuits. Repair as necessary.
Replace bad integrated control module.
None
Locate and correct gas interruption.
Replace or realign igniter. Igniter is fragile;
handle gently.
Check flame sense signal. Sand sensor
with emery cloth if coated and/or
oxidized.
Check flue piping for blockage, proper
length, elbows and termination. See
"Vent/Flue Pipe."
Verify proper induced draft blower
performance.
Check circulator blower speed and
performance. Correct speed or replace
blower, if necessary.
Replace induced draft blower pressure
switch.
Repair short.
Inspect pressure switch hose. Repair, if
necessary.
Inspect flue for blockage, proper length,
elbows and termination. Correct as
necessary.
Correct pressure switch setpoint or
contact motion.
Tighten or correct wiring connection.
Check primary limit switch. Replace, if
necessary.
Check filters and ductwork for blockage.
Clean filters or remove obstruction.
Check circulator blower speed and
performance. Correct speed or replace
blower if necessary.
Tighten or correct wiring connection.
33

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