Service Manual

Is the blocked vent
switch in the normal
closed position?
Does blower
energize?
(For Direct Spark
Ignition models,
ensure control display
shows “Heating”, raise
temperature setpoint if
necessary)
Is there 120VAC
across the white and
black wires at the
blower?
(see photo at right)
Replace blower.
(see “Blower
Replacement
Procedure”)
Y
N
Refer to ignition module/
control board illustration.
Is there 120VAC between
P7(5) and P7(3)?
Repair/replace
wire harness.
Y
Replace ignition
module/control
board.
Y
N
N
N
Is there 120VAC
across the top white
and bottom black wire
at the power switch ?
Y
N
Correct safety circuit
problem per safety circuit
trace
(section “Blocked Vent
Safety Switch Testing”).
Y
Y
Is there 120VAC
across the white and
black wires at location
P3 on the control
board ?
(see photo at bottom)
N
N
Refer to ignition module/control board
illustration.
Is there 120VAC between P7(5) and P7(3)?
Y
Replace
ignition module/
control board.
Call technical
support.
Check amp draw through
BLACK wire lead from
power switch to control
board. Is there .6 to 3.0
amps?
Replace blower.
(see “Blower Replacement
Procedure”)
N
Y
Is Blower wheel secured to
blower motor shaft?
N
Y
Determine
power
source
problem
and
correct
38
Checking for 120VAC
(Black & White Wires)
12
3
8
6
5
4
3
1
12
1
4
1
3
3
2
1
1
5
3
P2P4P5 P7P3
CONTROL BOARD
P10P9J1
DIRECT SPARK IGNITION MODELS
Is the flow switch in
the closed position?
Y
Correct safety circuit
problem per safety
circuit trace
(section “Flow Switch
Testing”).
N
Is the damper in
the open position?
Inspect Damper
(section “Damper
Testing”).
N
Y
Black wire leading to control
board from power switch
looped through amprobe.
38