11
EN
Furnaces
– If the system does not ignite and the thermostat remains closed on units with an external relay, the
blower will remain on until the thermostat is reset manually. Units with the relay on the ignition
control will shut the blower off even if the thermostat contacts remain closed. If the
thermostat is not reset within one hour, the system will try the ignition cycle again.
8. When the thermostat senses that the desired room air temperature contact is open, it will shut off power from
the ignition system and shut off the gas valve. The blower continues to run until the relay opens the circuit
(approximately 90 seconds), shutting off current to the motor.
I
On newer controls, a diagnostic error code light has been added. By counting the flashes of the light, an
error code can be determined. See the Code Failure Table for code failure information.
Code Failure Table
Number of Flashes
Diagnostic
Information
Explanation/Recommended Action
One (1) Flash with
Three-second (3) Pause
Airflow/Limit Fault Fan is running. No power is present at the air flow terminal
on the board. Potential cause are:
• Sail switch is not closing
• Limit switch is open
• Fan is not turning fast enough to close the sail switch
Check for voltage issues (see page 29) or a bad fan
motor (see page 23).
Two (2) Flashes with
Three-second (3) Pause
Flame Sense Fault The board is not sensing a flame.
Check for a faulty circuit board (see page 19) or a
defective electrode (see page 22).
Three (3) Flashes with
Three-second (3) Pause
Ignition Safety Lockout The furnace attempted ignition three times and failed to
light. The failed attempts caused a one-hour so safety
lockout of the furnace.
No Flashes, Steady Light Internal Control Failure Check for a faulty circuit board (see page 19).
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