Bradford White U-TW4-75S-76R-3N - Manual (Page 26)

Page 26
Pressure Switch Testing (cont’d)
Pressure Switch Testing
Pressure switch
wire leads
With steps 1,2 & 3
complete, discon-
nect wire leads
from pressure
switch.
Use a multi-meter
set to the ohms
setting. With
blower off, check
across the pres-
sure switch termi-
nals. Are the
switch contacts
open (no electrical
continuity)?
Position the gas
control power
switch to the “ON”
position and adjust
the thermostat to
call for heat. This
will start the
blower. Check with
the multi-meter.
Do the pressure
switch contacts
close with the
blower running?
The switch contacts
are OK. See safety
circuit trace (page
40).
Check the tubing and
pressure tap on switch
for blockage. Is there
a blockage?
Check the tub-
ing and pressure
tap on switch for
blockage. Is
there a block-
age?
Clear blockage
Replace switch
(see page 27).
Is the vent
system
blocked?
Is vent system
length within the
vent table specifi-
cations listed on
pages 9 & 10?
Reconfigure vent
system to be
compliant with
vent tables.
See blower
testing (page
28). Is the
Blower OK?
Correct the
blower prob-
lem.
Y
N
N
N
N
N
N
Y
Y
N
Y
Y
Y
26