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PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER
ENERGIZES, IGNITOR IS ENERGIZED.
Condition Possible Cause Corrective Action/Comments
4.1
− Unit operates with a cooling and
continuous fan demand.
Combustion air inducer energizes
4.1.1
Check that gas is being supplied to
the unit.
ACTION 1 − Check line pressure at the gas valve.
Pressure should not exceed 13" WC for both nat-
ural and propane. Line pressure should read a
minimum 4.5" WC for natural and 8.0"WC for pro-
pane.
−
zes
with Heating demand.
− Ignitor is energized but unit fails to
light.
4.1.2
Miswiring of gas valve or loose-
connections at multi−pin control amp
plugs or valve.
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
4.1.3
Defective gas valve or ignition
control.
ACTION 1 − Check that 24V is supplied to the gas
valve approximately 35 seconds after heat de-
mand is initiated.
ACTION 2 − Replace the valve if 24V is supplied
but valve does not open.
ACTION 3 − Replace the control board if 24V is not
supplied to valve.
PROBLEM 5: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY
Condition Possible Cause Corrective Action/Comments
5.1
5.1.1
Low pressure differential at the prove
switch.
ACTION 1 − Check for restricted intake and ex-
haust vent. Remove all blockage.
ACTION 2: Check for proper vent sizing. See
installation instructions.
− Burners fire with a heating demand.
− Burners light but unit shuts off prior
to satisfying T−stat demand.
− Diagnostic lights flash the pressure
5.1.2
Wrong concentric vent kit used for ter-
minating the unit.
ACTION 1 − Check vent termination kit installed.
See Placement and Installation section.
−
e pressure
switch code.
LED#1−Off
5.1.3
Condensate drain line is not draining
properly.
ACTION 1 − Check condensate line for proper
vent slope, and any blockage. Condensate
should flow freely during operation of furnace. Re-
pair or replace any improperly installed conden-
sate lines.
LED#2−Slow Flash
5.1.4
Low pressure differential at the prove
switch.
ACTION 1 − Check for restricted intake and ex-
haust. Remove all blockage.
ACTION 2: Check for proper vent sizing. See
installation instructions.
5.2
− Combustion air inducer energizes
with a heating demand.
B rners light b t fail to sta lit
5.2.1
Sensor or sense wire is improperly
installed.
ACTION 1 − Check that sensor is properly lo-
cated and that the sense wire is properly at-
tached to both the sensor and the control.
− Burners light but fail to stay lit.
− After 5 tries the control diagnostics
flash the watchguard burners failed to
ignite code.
5.2.2
Sensor or sense wire is broken.
ACTION 1 − Check for a broken sensor.
ACTION 2 − Test continuity across the sense
wire. If wire or sensor are damaged replace the
component.
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
5.2.3
Sensor or sensor wire is grounded to
the unit.
ACTION 1 − Check for resistance between the
sensor rod and the unit ground.
ACTION 2 − Check for resistance between the
sensor wire and the unit ground.
ACTION 3 − Correct any shorts found in circuit.
5.2.4
Control does not sense flame.
ACTION 1 − Check the microamp signal from
the burner flame. If the microamp signal is be-
low normal, check the sense rod for proper
location or contamination.
ACTION 2 − Replace, clean, or relocate flame
sense rod. If rod is to be cleaned, use steel
wool or replace sensor. DO NOT CLEAN ROD
WITH SAND PAPER. SAND PAPER WILL
CONTRIBUTE TO THE CONTAMINATION
PROBLEM. NOTE: Do not attempt to bend
sense rod.
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