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Trouble Shooting Instructions:
Furnace
Ignition Control Diagnostic LED
During normal operation, the LED is shut off. The LED will be on
or flashing during a fault condition. If a fault condition is
occurring, turn the unit off and on again. If the LED is still
flashing, refer to the following troubleshooting section.
LED Indication Error Mode
Steady on Internal control failure
1 flash Air flow fault
2 flashes Flame with no call for heat
3 flashes Ignition lockout
Airflow Fault (1 Flash)
An airflow fault may be occur for the following reasons:
• An airflow switch continually monitors the combustion airflow during an ignition sequence. During the
initial call for heat, if the pressure switch contacts are in the closed position for 30 seconds without an
output to the combustion blower, an airflow fault will be declared. The control will remain in this mode with
the combustion blower off.
• After the combustion blower output (L1 and IND) is energized and the airflow switch remains open for
more than 30 seconds, an airflow fault will be declared. The control will stay in this mode with the
combustion blower on, waiting for the airflow switch to close.
• If the airflow signal is lost while the burner is firing, the control will immediately de-energize the gas valve
and the combustion blower will remain on. If the call for heat remains, the control will wait for proper
airflow to return. If proper airflow is not detected after 30 seconds, an airflow fault will be declared. If
proper airflow is detected at any time, a normal ignition sequence will begin.
Once proper airflow is detected, the normal Sequence Of Operation for ignition will follow. See Start-Up
Instructions for the furnace in this manual.
Flame Fault (2 Flashes)
If the main valve fails to close completely and maintains a flame, the full-time flame sense circuit will detect it
and energize the combustion blower. Should the main valve later close completely and remove the flame signal,
the combustion blower will be de-energized.
Ignition Lockout (3 Flashes)
Possible Cause Solution
Manual gas valve not open Open manual valve
Air in the gas line Bleed gas line
Supply gas pressure too high or too low Check that supply pressure is between 6 in. wc and 14 in. wc for
natural gas and 11 in. wc and 14 in. wc for LP.
Loose wire connections Check for tight wire connections.
No spark:
a. Transformer failure a. Check primary and secondary voltages of transformer. Replace
if necessary.
b. Spark electrode b. Ensure spark gap is
1
⁄8 in. and ceramic insulator is not cracked.
Replace if necessary. Electrode is NOT field-adjustable.
c. Spark cable shorted to ground c. Replace spark cable.
e. Ignition controller not grounded e. Check that the ignition controller is grounded to the furnace
control center.
High limit control tripped Check unit airflow and manifold pressure.
Faulty combination gas valve If 24 volts is measured between terminals MV and common, but
valve remains closed, replace valve.
Faulty ignition control Check diagnostic LED for steady on and for voltage between V1
and V2. If no voltage is present, replace ignition control.
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