No
Yes
Call for heat.
Thermostat (W to R)
contacts close.
No
No
No
Yes
Yes
Yes
Yes
Replace open fuses
in 120 volt supply.
Energize system and
check for proper
operation
No
Check wiring. If OK,
replace module.
Energize the system
and check for proper
operation.
Replace thermostat.
Energize system and
check for proper
operation.
Energize system and
check for proper
operation.
Replace transformer.
Energize system and
check for operation.
No
No
Yes
Yes
Check wiring. If OK,
replace module.
Energize the system
and check for proper
operation.
Check wiring. If ok,
replace thermostat.
Energize system and
check for proper
operation.
Correct breaks in
igniter harness or
connections.
Energize & check.
Continue to
Main Burner
Ignition Section
Yes
Disconnect electric
power to system at
main fuse or
circuit breaker.
Replace igniter. Connect
electric power to system
at main fuse or circuit
breaker.
System is
functioning
properly.
Connect voltmeter
across terminals of
igniter harness.
Check wiring. If ok,
replace thermostat.
Energize system and
check for proper
operation.
No
No
Yes
Yes
No
Yes
No
PREPURGE/IGNITOR WARM-UP
Check for proper
operation on pressure
switch contacts. Replace
inducer blower or
pressure switch.
Energize system
and check for
proper operation
Pressure switch
stuck open.
Is the inducer
blower on?
Is diagnostic
indicator flashing
3 times?
Is diagnostic
indicator flashing
2 times?
Is
25 volts present
across terminals
W & C?
Is
25 volts present
across terminals
R & C?
Is
25 volts present
across secondary of
transformer?
Is
120 v present
across primary of
transformer?
Does silicon
igniter warm up and
glow after purge
duration?
Unplug
igniter from wire
harness and connect
ohmmeter across igniter
leads. Is resistance
between 20 & 1000
ohms?
Energize
system. Does Igniter
turn off after flame
sensed?
Check
for 120 v across
ignition harness terminals
after purge duration. Is
120 v present?
650.69-N3
Unitary Products Group
17
