50A50 Flow Chart 3 - American Standard *UD Series Operation Manual

50A50 Flow Chart 3

Inducer Draft Motor
and Pressure
Switch Check
3C
NO
Repair low
voltage wiring
fault. 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.
3A
Call for heat.
Thermostat
contacts
R & W close.
3B
YES
Is 24V
present at Is Diagnostic
control terminals
W & B/C?
YES
3D
YES
Is Diagnostic
Replace control.
Check for operation.
continuously?
3E
NO
Is Diagnostic
Go to Chart 1
Step 1G.
3F
YES
present across
Replace inducer
control terminals
draft motor.
Check operation.
3G
wiring to one
Replace pressure
side of pressure
switch. Check
switch. Does inducer
operation.
YES
3H
NO
Replace control.
control terminals
Check operation.
Replace inducer
draft motor. Check
3I
YES
Is induced
Is diagnostic
draft motor
LED flashing
energized?
3 times?
NO
3J
Jumper
pressure
LED flashing
switch.
slowly?
NO
3K
Does ignitor
LED on
glow?
NO
3L
Place incline
manometer in
series with
LED flashing
pressure switch
3 times?
tubing.
YES
3M
Is 120V
Is pressure
greater than
pressure switch
IND & IND
specs.
NEUTRAL?
NO
3G
Unplug
Remove vent
connector
from furnace
energize?
flue collar.
NO
3O
Is 120V
Is pressure
present at
greater than
pressure switch
IND & IND
specs.?
NEUTRAL?
YES
Repair leaks in
inducer assembly or
replace induced draft
motor. Check operation.
operation.
Note: Check diagnostic LED light flash rate through view
port in blower door before removing blower door!
53
NO
YES
NO
YES
YES
Replace pressure
switch. Check
operation.
NO
NO
Correct blocked
or incorrectly
installed vent.
Check operation.
NO