Instruction manual
78
25 INVALID MODEL SELECTION OR
SETUP ERROR – If status code 25 only
flashes 4 times on power-up the control is
missing its model plug PL4 and is
defaulting to the model selection stored in
memory. If status code 25 flashes
continuously it could indicate any of the
following:
- Model plug PL4 is missing and there is
no valid model stored in permanent
memory. This will happen if you forget
to install the model plug PL4 on a
service replacement control.
- Thermostat call with SW1-1 ON.
- Thermostat call with SW1-6 ON.
-SW1-1andSW1-6bothON.
- Two different furnace models twinned.
- Service replacement control is incorrect.
Need modulating board with software
version V17 or later.
31 MEDIUM PRESSURE SWITCH, HIGH
PRESSURE SWITCH, OR PSR RELAY
DID NOT CLOSE OR REOPENED -
Check for:
- PSR relay may be defective.
- See status code 32.
41 BLOWER MOTOR FAULT – Indicates the
blower failed to reach 250 RPM or the
blower failed to communicate within the
prescribed time limits. Thirty seconds
after being turned ON or ten seconds
during steady-state operation. Turn power
off and check the following items first
before proceeding to the next step.
- Rubbing blower wheel.
- Loose blower wheel.
- Wiring from furnace control to blower
motor.
Remove the R thermostat connection from
the furnace control, disconnect both
connectors from the blower motor PL13
and PL14. Does the blower wheel turn
freely?
Replace the blower control module attached to
the blower motor. Follow the instructions with
the blower control module to make sure the
entire blower motor does not need to be
replaced.
Turn power back on. Is there 115VAC at
PL14-5 and PL14-4?
Youhaveanopenwireorbad
terminal on either the BLACK or
WHITE power leads between
the furnace control and the
blower motor. If you have a
power choke disconnect it and
check continuity.
YES
YES
NO
NO
Is there 12-VDC at PL13-1 RED (+) and
PL13-4 GREEN (-)?
YES
NO
Is there 12-VDC at PL3-1 RED (+) and
PL3-2 GREEN (-)?
Replace the furnace control.
NO
Youhaveanopenwireorbad
terminal on either the RED or
GREEN wire between the
furnace control and the blower
motor.
YES
Is there 5-VDC at PL13-2 YELLOW (+)
and PL13-4 GREEN (-)?
Is there 5-VDC at PL3-3
YELLOW (+) and PL3-2
GREEN (-)?
NO
NO
Youhaveanopenwireorbad
terminal on the YELLOW wire
between the furnace control and
the blower motor.
YES
YES
The voltage just measured should be
very stable and should not fluctuate more
than .02-VDC. If the voltage fluctuates
more than this get a different voltmeter
before proceeding.
Turn power off, disconnect PL13 and
PL14 from the blower motor, then turn
power back on. Connect a DC voltmeter
across PL13-3 BLUE (+) and PL13-4
GREEN (-). The voltage should be near
0-VDC but it will fluctuate briefly several
times a second. If you have an analog
voltmeter the needle will briefly go high
several times a second. If you have a
digital voltmeter with a bar graph it will
show a large change in magnitude on the
bar graph several times a second. If you
have a standard digital voltmeter it will
show a brief fluctuation in voltage and the
magnitude may vary depending on the
voltmeter used.
Does the voltage fluctuate as described in the
previous step?
Connect a DC voltmeter across PL3-4 BLUE
(+) and PL3-2 GREEN (-). Does the voltage
fluctuate as described two steps back?
You have an open wire or bad terminal on the
BLUE wire between the furnace control and the
blower motor.
NO
Replace the furnace control.
YES
Turn power off, reconnect PL13 and
PL14 to the blower motor, then turn
power back on. Connect a DC voltmeter
across PL3-3 YELLOW (+) and PL3-2
GREEN (-). Does the voltage fluctuate
more than it did in the previous step?
NO
YES
YES
NO
Replace the blower control module attached to
the blower motor. Follow the instructions with
the blower control module to make sure the
entire blower motor does not need to be
replaced.
42 INDUCER MOTOR FAULT – Indicates the
inducer motor has not started within 20
seconds after a call for heat, the inducer
motor RPM is outside its valid range of
operation, or the inducer RPM signal was
lost for 5 seconds during operation.
Check for:
- Proper vent sizing.
-Failedinducermotor.
- Restricted combustion air supply.
- Improper motor wiring.
35 GAS VALVE FAULT – Indicates the
modulating gas valve failed to respond to
a command from the furnace control or
power to the gas valve electronics was
interrupted. Check for:
- Intermittent RED, YELLOW, or
ORANGE wire at gas valve or PL8
connections.
A11290C
987MA