Furnace Fails to Operate Properly
Review "Sequence of Operation" and visually inspect the
following before troubleshooting:
Electrical Shock Hazard
Disconnect power before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical shock.
Is the integrated ignition/blower control board and power to
the furnace on?
Is the blower compartment door securely closed?
Are the manual shutoff valves in the gas line to the furnace
Are all wiring connections secure?
Start the system by setting thermostat above room temperature.
Observe system response. Then use the information provided in
this section to check the system operation.
Fault Code History Button
The control stores the last 5 fault codes in memory. A push-
button switch is located on the control. When the push-button
switch is pressed and released, the control flashes the stored
fault codes. The most recent fault code is flashed first; the oldest
fault code is flashed last. To clear the fault code history, press
and hold the push-button switch for more than 5 seconds before
High Heat State LED
On these models, a green LED is provided on the control board to
indicate high heat state.
High Heat State—Green LED
No demand for high heat
High heat demand, operating normally
High heat demand, high pressure switch not
On these models, an amber LED is provided on the control board
to display CFM. To determine what CFM the motor is delivering at
any time, count the number of times the amber LED flashes. Each
flash signifies 100 CFM; count the flashes and multiply by 100 to
determine the actual CFM delivered (for example: 10 flashes x
100 = 1,000 CFM).
The furnace has a built-in, self-diagnostic capability. If a system
problem occurs, a fault code is shown by a red LED on the
control board. The control continuously monitors its own
operation and the operation of the system. If a failure occurs, the
LED will indicate the failure code.
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
Failure Codes Chart
No power to control or control hardware
Flame present with gas control valve off
Pressure switch closed with inducer off
Low-fire pressure, rollout, drain pressure,
or auxiliary limit open
High limit switch open
Pressure switch cycle lockout
Lockout due to no ignition
Lockout due to too many flame dropouts
Incorrect polarity and phasing