Service Procedure V: Blower Testing And Replacement - Bradford White UCG100H3993N Service Manual

Does blower energize?
Ensure control display
shows "Heating." Raise
temperature setpoint if
necessary.
N
Is there 120VAC across
the white and black
wires at the incoming
power harness
connection (see photo
at right)?
Call for
Y
technical
support.
Y
Refer to ignition
module/control board
illustration. Is there 24VAC
between blue and yellow
wires at location J8?
Y
Is there 120VAC
across white and
black wires at the
blower? (See
photo at right.)
Y
Replace blower. (See
"Blower Replacement
Procedure".)
28
Service Procedure V:
Blower Testing and Replacement
Is collector high limit
switch in normally closed
Y
position?
N
Determine
power
N
source
problem
and
correct
Is blower wheel
Y
secured to blower
motor shaft?
N
Replace blower. (See
"Blower Replacement
Procedure".)
Is collector high limit
N
switch in normally
closed position?
Correct safety circuit
problem per safety
circuit trace. (See
Blocked Vent Pressure
Switch Testing".)
N
Repair/replace wire
harness.
Refer to ignition
module/control board
Y
illustration. Is there
24VAC between blue
and yellow wires at
location J8.
Y
120 VAC
power
connection
Check amp draw
through BLACK wire
lead of blower motor. Is
there .6 to 3.0 amps?
N
Black wire
leading to
blower looped
through amp
probe
Replace ignition
Y
module/control
board.
N
28
N
Replace ignition
module/control board.
120 VAC check
at blower