Manual

23
Two Times Air proving switch contacts do not close during a call for heat.
Are air proving
switch contacts
stuck open?
(Perform continuity
check.)
Does
fan motor start up
for prepurge
during initial call
for heat?
Is
fan wheel
binding?
Is
fan wheel loose
on motor
shaft?
Yes
Yes
Yes
No
Check for binding of flapper on housing. Repair or replace as necessary.
Yes
Yes
Check for proper clearance of fan wheel to motor mount. If good, check for housing alignment. If necessary replace fan.
Tighten fan set screws securely to flats of motor shaft.
Yes
Clean the fan wheel with compressed air or soft brush.
Defective motor or capacitor.
Yes
Remove obstruction. Clean as necessary.
No
Is
fan wheel
plugged with
dirt?
No
Is
there an
obstruction
in blower outlet
preventing air switch
closure?
No
Is
line voltage
supplied to motor
from ignition
module?
No
If Improper voltage is supplied,
contact electrician.
- OR -
If no voltage is supplied to motor,
check wiring, or replace ignition
control module.
No
Yes
Are
24 volts
sent to air
proving
switch?
Check wiring between ignition
control module terminal PSI and
and air proving switch. Repair or
replace as necessary. If wiring is
good replace ignition control.
No
No
With motor in operation, check for 24 volts from terminal PSI and at terminal PSO at the control module. If 24 volts is sent from PSI, but not received from the air provng switch at PSO, replace the air proving switch.