20
EN
Furnaces
Component Diagnostic Question Action Based On Status Page
Is there power at the thermostat
terminal on the board?
No =
• Confirm the thermostat is calling
for heat
• Confirm there is power at
the thermostat and at the air
conditioner control box
18
Is there power going out to the fan
motor?
No = Check the sail switch
• If the sail switch is stuck in the
closed position, replace the sail
switch
• If the sail switch is not stuck
in the closed position, check
the power at the thermostat
terminal and the air flow
terminal on the board. Replace
the board if you have proper
voltage at both terminals
38
Is there power at the air flow
terminal on the board?
No = Check for continuity
• If the limit switch is stuck open,
replace the limit switch
• If the sail switch is stuck open,
replace the sail switch
35
38
Is there power to the gas valve
from the circuit board within 15
seconds of power arriving at the
airflow terminal?
No =
Check the board. Replace if bad
Check the electrode for a short.
Replace if a short has occurred
32
34
Does the burner ignite then turn
off?
Yes = Verify that there are no
cracks in the ceramic on the
electrode, or any shorts in
the high-tension lead to the
electrode
34
Does the burner ignite when the
blower is running?
No=
• Improper ground.
Perform maintenance
• Edge connector or circuit board
is dirty. Perform maintenance
41
Is there an error light on the
control board?
Yes = Check the error codes for the
appropriate furnace in the
sequence of operation/wiring
diagrams
9
Is the gas valve opening but not
getting a spark?
Yes = Remove the electrode wire
from the ignitor. Hold the wire
close to the ignitor, using a pair
of insulated pliers. If it sparks,
replace the electrode
34
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