50A51 Flow Chart 3 - American Standard *UD Series Operation Manual

50A51 Flow Chart 3

3A
NO
Is diagnostic
LED flashing 3
times?
YES
Jumper
pressure
switch 1.
NO
Does igntor
glow?
YES
Place incline
manometer in series
with pressure
switch tubing.
Is
YES
pressure
greater than
pressure switch
1 specs?
NO
Remove vent
connector from
furnace flue
collar.
YES
Is pressure
greater than
pressure switch
1 specs.?
NO
Repair leaks in
inducer assembly or
raplace induced draft
motor. Check
operation.
CAUTION: If diagnostic indicator (LED) shows five (5) flashes,
turn off gas supply at source before disconnecting electrical power.
Failure to do so may result in personal injury or fire.
Diagnostic
LED flashing fast
(2 times per second)
continuously.
3B
Turn power OFF to
furnace. Unplug ignitor
from wire harness. Connect
voltmeter across ignitor
wiring harness leads from
control. Energize system.
YES
Replace ignitor.
Check operation.
YES
Replace broken or
defective wiring. control term IGN &
Check operation. IGN NEUTRAL?
Replace pressure
Replace control.
switch 1. Check
Check for operation.
operation.
YES
Purge system of
pressure adjusted
air. Energize system.
Check operation.
Adjust manifold
Correct blocked
to required pressure
or incorrectly installed
vent collar.
YES
Does ignitor
Does burner
warm up and
ignite?
glow?
NO
3C
valve manual
knob in ON
position?
Turn manual knob to OFF
position. Connect
Is 120V
manometer to outlet
present at
pressure tap. Turn knob
ignitor leads?
to on position.
Energize system.
NO NO
3D
Is 120V
Is outlet
present at
pressure detected
after ignitor warm
up time?
NO
Refer to service
facts or installers
guide for proper
pressure settings.
Is
manifold
Replace gas valve.
Energize system.
to required
Check operation.
rating?
NO
Replace control
module. Check
setting. Check
operation.
operation.
Note: Check diagnostic LED light flash rate through view
port in blower door before removing blower door!
58
YES
NO
NO
Is gas
Turn manual knob
to on position.
Check operation.
YES
Restore gas
supply at source.
Check operation.
NO
Is gas at source?
YES
3E
Connect voltmeter
to gas valve leads.
Energize system.
YES Is 24V
present across
gas valve term 1 & 2
after ignitor
warm up?
NO
Is 24V
present across
MVL & MV-COM term
after ignitor
warm up?
Repair or replace
broken leads to gas
valve. Check
operation.
NO
YES
NO
YES