110
Airflow
Signal was not received from air switch
when supply blower was running.
Verify supply fan operation, refer to
“Start-Up Procedure” on page 79
Check damper operation.
Check airflow switch and tubing at the
MUA board.
FSC1 High Temp
The Flame Safety Controller (FSC)
continually and safely monitors, analyze,
and controls the proper operation of the
gas burner and inducer motor.
Check connector J7 on the MUA board.
Make sure the connection is secure.
High limit switch failed open. There
should be continuity.
FSC1 Rollout
If flame-rollout is present, the switch de-
energizes heater circuit on individual
furnace. Must be manually reset by
pressing the small button on the switch.
Check wiring to the switches.
Reset the switch.
Rollout switch failed open. There should
be continuity.
Check for a blocked tube, low airflow, or
low gas pressure.
FSC Vent Proving
The FSC verifies that airflow is sensed by
the induced draft air sensor.
Kinked/blocked/damaged hose.
Blockage in vent system. Poor venting.
Check bleed hole in proving switch.
Clogged condensation drain.
Power vent motor.
Failed vent proving switch.
Refer to
.
Min Low Pressure
Limit
The suction pressure for the compressor
is below the minimum threshold in
software.
Follow possible checks for “Refrigerant
Low PS”.
Refrigerant Low PS
If the system is operating at a low
pressure and temperature range, the
system can become inoperable.
Verify low pressure switch operation.
Low Refrigerant. Refer to
Refrigerant High PS
If the system is operating at a high
pressure and temperature range, the
system can become inoperable.
Verify high pressure switch operation.
Faulty condensing fan motor.
Outside coil plugged.
Inadequate airflow across coil.
Blockage in the system. Refer to
“Monitoring the A/C System” on
Refrigerant
DSCHRG Temp
(Heat Pump)
Discharge temperature is out of range. Follow possible checks for “Refrigerant
High PS”.
Problem
Potential Cause
Corrective Action
