27
*SD FAULT CODES AND TROUBLESHOOTING GUIDE
ALARM
ALARM
EXPLANATION
LED
BOARD
DISPLAY
TROUBLESHOOTING
DESCRIPTION
Internal
Failure
Error
Frequency out
of Range
E01
1. Check for low input voltage.
2. Powering the furnace with generator could
cause this error. Check for loose incoming
power wires.
Voltage Frequency is out of range. The control
board monitors the voltage frequency and will
allow 56-64 Hz for normal operation.
External
Lockout
Ignition Retry
Exceeded.
Failure to ignite
5 times.
E2.1
Look through sight glass to see if its lighting gas.
1. Does the unit light? If yes, then the flame sensor
could be dirty or damaged or the wiring between
the board and the flame sensor is damaged.
2. If the unit is not lighting, check the gas valve
and ignitor. Possible issues: Faulty gas valve,
ignitor bad, gas valve switch off, wire(s) not
connected, check the gas supply
The control will try to establish flame the initial
try plus 4 re-tries. The control will display E2.1
after 5 tries to light during the same heat call.
Recycles exceeded.
Limit or pressure switch
opening 10 times
during heat operation
E2.2
Intermittent opening of limit or pressure switch
1. Check for loose wiring at all switches.
2. Check all pressure and limit switches for
function.
3. Check for low airflow which could trip a limit
before the thermostat setting is satisfied.
Once flame has been established, the control
monitors that all pressure switches and limits are
closed. If any switch opens for at least 2 seconds
the control will stop the heat sequence and will
initiate post purge. The control will recycle the
heat sequence 10 times if a pressure switch or
limit switch opens and there is still a call for heat.
After the 10th recycle the control will display
E2.3. If the call for heat is satisfied in the recycle
sequence, the recycle count will start over.
Internal
Control
Fault
E2.3
Internal relay in the control board has failed-
Replace the board.
Control senses 24V output to the gas valve. If
voltage is not sensed to the gas valve, the control
will display E2.3.
HLO Relay on
control board
failure to energize
10 times. Internal
Control Fault
E2.4
Internal relay in the control board has failed-
Replace the board.
Relay on the board is not supplying 24V. The
control monitors 24V outputs to internal relays. If
the HLO output is not energized after 10 retries,
the control will display E2.4. - Replace the board
Open Pressure
Switch #2
Recycles Exceeded
5 tries
E2.6
1. Check for a blocked restricted vent.
2. Check the Inducer Pressure Switch #2 and
Collector Switch to be faulty or stuck open. Refer to
the wiring diagram for Pressure Switch #2 wiring.
Pressure switch #2 detected open 5 times in the
same call for heat. Once flame is established,
after 35 seconds the control will start to monitor
the inducer pressure switch #2 and the collector
switch. If either switch open during operation, the
control will intiate the post purge sequence and
then restart the ignition sequence. If the inducer
pressure switch #2 or the collector switch open
in the same call for 5 heat times, the control will
display E2.6.
Pressure
Switch 1
Error -.5"WC
Pressure Switch #1
closed at intial
call for heat
E3.1
1. Check inducer pressure switch #1 to be closed.
The control checks at the beginning of the heat
cycle to see if pressure switch #1 is open. If open,
the heat cycle proceeds. If pressure switch #1
is closed, Error 3.1 is reported
Pressure Switch #1
opens during heat
cycle
E3.2
1. Check for loose wires at Pressure Switch #1.
2. Faulty switch
3. Check for a blocked inlet on top of the furnace.
4. Check the inlet air orifice for debris.
5. Check the hose for damage.
The control monitors pressure switch #1(PS1
on the board) during the heat cycle, if pressure
switch #1 opens for more that 8 seconds, the
heat cycle ends and E3.2 is reported
Table 6. *SD Fault Codes
