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Troubleshooting - Whirlpool WFCU Installation Instructions Manual

90+ gas furnace
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Furnace Fails to Operate Properly
Review "Sequence of Operation" and visually inspect the
following before troubleshooting:
Is the power to the furnace on?
Is the blower compartment door securely closed?
Are the manual shutoff valves in the gas line to the furnace open?
Failure Codes
The system has a built-in, self-diagnostic capability. The control
continuously monitors its own operation and the operation of the
system. If a system problem occurs, a failure code is indicated by
the LED on the gas control valve. See the Failure Codes chart for
a description of the flash codes.
IMPORTANT: Do not remove the blower compartment door or
turn off the power to the furnace because either action will clear
the control's memory of the failure.
1. Start the system by setting the thermostat above the room
2. Observe the system's response.
3. Use the information provided in this section to check the
system's operation.
Failure Codes
LED Status
Fault Description
(Flash Codes)
No Power to the System Control
Steady Flash
Normal Operation (Standby or call for heat)
(11 or more
without a
2 Flashes
Pressure switch closed when it should be
Pressure switch stuck open 30 seconds or
longer after call for heat (system in 5-minute
delay mode before next call for heat). On/off
3 Flashes
switch in OFF position during a call for heat
will generate this code.
4 Flashes
Open Limit Switch or Limit Switch Circuit
5 Flashes
Flame Sense Signal sensed out of proper
*6 Flashes
Soft Lockout Type 1
Failure to light within 4 trials for ignition
1 Flash
(See Note 1)
*6 Flashes
Soft Lockout Type 2
Flame sense lost during run
2 Flashes
(See Notes 1 & 2)
*6 Flashes
Soft Lockout Type 3
Pressure switch opened during run
3 Flashes
(See Notes 1 & 2)
*6 Flashes
Soft Lockout Type 4
Limit or limit circuit opened during run
4 Flashes
(See Notes 1 & 2)
*6 Flashes
Soft Lockout Type 5
Flame has gone away after Error Code 5
5 Flashes
(See Note 1)
*6 Flashes
Soft Lockout Type 7
Self-check failure
7 Flashes
(See Note 1)
*10 Flashes
Line Input Voltage Polarity Reversed
*On some models
Note 1: The 6 + X designation indicates a combination of flash
codes. Six flashes shows the control is in soft lock-out,
followed by X flashes to indicate the reason the control went
into soft lockout. When the 6 + X code is flashed, the control
will attempt a new ignition sequence after 1 hour (if the call for
heat is still present). Reset of the thermostat will initiate a new
ignition sequence immediately.
Note 2: Any combination of 5 "abnormal events" during a
single call for heat will result in a soft lockout. An abnormal
event is an occurrence of any of the following: flame sense
failure during run, airflow proving circuit open during run, or
limit circuit open during run. The flash code will indicate which
was the last abnormal event that put the system into the soft
lockout state (see above).


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