TROUBLESHOOTING
35
Symptom
LED Status
Fault Description
Corrective Actions
Furnace operates at reduced
performance or operates on
low stage when high stage is
expected
Airflow is lower than demanded
Check filters for blockage, clean filters or remove
obstruction
Check ductwork for blockage, remove
obstruction and verify all registers are fully open
Verify ductwork is appropriately sized for system,
resize and/or replace ductwork if necessary
Furnace fails to operate
1
Analog Pressure Sensor
Reference Error. APS reference
is out of the range (5.0+/-0.2)V
for 5 seconds
Verify electrical connections to pressure sensor
Furnace fails to operate
1
Analog Pressure Sensor Null
Error. Inconsistent Pressure
reading with inducer OFF
Verify electrical connections to pressure sensor
Furnace fails to operate
1d
Analog Pressure Sensor Span
Error. Inconsistent pressure
reading with inducer ON
Verify electrical connections to pressure sensor
Furnace fails to operate
1
Analog Pressure Error (Blocked
Vent Error)
Need to check the APS Sensor or its connection
if this error is occurred. The failure conditions
occur as per the following for 5 seconds:
1. The vent is blocked, and the pressure could not
reach (lower than)
the target pressure when inducer stayed at
maximum RPM which
stored in Shared Data.
2. The vent is blocked, and the pressure could not
reach (higher than)
the target pressure when inducer stays at the
minimum RPM
(Pressure Switch Min Limit).
3. APS fault causes the pressure fixed at a value
lower than the target
pressure when inducer stayed at maximum RPM
which stored in
Shared Data.
4. APS fault causes the pressure fixed at a value
higher than the target
pressure when inducer stayed at minimum RPM
(Pressure Switch
Min Limit).
Furnace fails to Operate
1
Analog Pressure Sensor, Input
Error
Check the APS Sensor or its connection if this
error is occurred. APS input voltage is out of the
below ranges for 5 seconds.
1. If 2" is selected, the voltage range shall be from
(0.25-0.06)V to (4+0.06)V.
2. If 4" is selected, the voltage range shall be from
(0.5-0.06)V to (4.5+0.06)V.
