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A91253
Is 24VAC
across pressure
switch N/O contact
& screw C on
board?
YES
NO
Is 24VAC
across pressure
switch N/O contact
& screw C on
board?
Is heat
exchanger
pressure drop greater
than 0.35-in.
wc?
Is
24VAC across gas
valve?
Is
unit lit?
Check/Replace:
1. Vent systems
2. Induce wheel
3. Flue choke
4. Inducer voltage
5. Inducer motor bearings
Check/Replace:
1. Limit switch
2. Limit shield (if used)
3. Fuse link
4. Auxillary limit switch (if used)
5. Wire harness
START
Disconnect all thermostat
wires from board.
Turn on 115-VAC
power to unit.
Is blower
running?
Is 24VAC
across screws
R & C?
Is 24VAC
across screws
W & C or
G & C?
Are
all thermostat
wires to board
disconnected?
Turn off 115-VAC
power to unit.
Replace
board.
Is
115VAC
across L1 &
L2?
Is
24VAC
across screws
R & C?
Is
115VAC
across HI &
COM?
Is
blower running
on cooling
speed?
Jumper across
screws R & G.
Is
115VAC
across EAC-1
& COM?
Replace
board.
Remove
R & G jumper.
Replace
blower motor
and/or start
capacitor.
Check/Replace:
1. Unit power
2. Door switch
3. Power harness
Check/Replace:
1. 3-amp board
fuse
2. Transformer
Check pressure
tube for leak or
crimp; otherwise,
replace pressure switch
Does
blower turn
off?
Jumper across
screws R & W.
Is
24VAC
across PL1-2
& screw C on
board?
Replace
board.
Repair wire
harness.
Check/Replace:
1. Draft safeguard switch
2. Wire harness
Check/Replace:
1. Pilot
2. Thermocouple
3. Gas valve
Is
inducer motor
on?
Replace
inducer motor.
Is
115VAC across
inducer motor
connector?
Is
blower running
on heat speed 45
sec after unit
lights?
Is
115VAC across
inducer motor
connector?
Is
115VAC
across EAC-1
& COM?
Is
24VAC across
PL-2 & screw
C on board?
Check/Repair
wire harness;
otherwise,
replace
pressure
switch.
Replace
board.
Remove
R & M jumper.
Repair wire
harness.
Is
24VAC
across
PL-1 & screw
C on board?
Replace
blower motor
and/or start
capacitor.
Replace
board.
Check/Replace
thermostat
and/or
thermostat wiring.
After
off-delay
does blower
turn off?
Reconnect all
thermostat wires.
Does unit
operate?
END OF TEST.
YES YES
NO
NO YES
NO
NO NO
YES
NO NO
YES
YES
NO
NO
YES
YES
YES
NO
NO
NO
NO
YES
YES
YES
YES
YESNO
NO
NO
NO
NO
NO
YES
NO
NO
NO
YES
YES
YES
YES
YES
NO
YES
YES
YES
YES
NO
NOTE: After replacing any component, verify correct operating
sequence as indicated by bold arrows.
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