Bradford White U-TW4-75S-76R-3N - Manual (Page 20)

U TTW SERVICE PROCEDURE IV
Pressure Switch Testing and
Replacement
Pressure Switch Testing WARNING
115 volt potential exposure. Use caution
making voltage checks to avoid personal injury. Step 1. Position gas control power switch to
the “OFF” position.
Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and
remove cover (see photos 1 and 2).
Step 3. Carefully remove pressure switch from blower housing (see photo 3).
3
Use a multi-meter set to the
ohms setting. With blower off,
check across pressure
switch terminals.
Are switch contacts open?
(no electrical continuity)
Check tubing and pressure tap
on switch for blockage.
Is there blockage?
Replace switch
(see page 21)
Position gas valve power
switch to the “ON” position
and adjust thermostat
to call for heat,
this will start the blower.
Check with multi-meter, do
pressure switch contacts close
with blower running?
With steps 1,2 & 3 complete,
disconnect wire leads from
pressure switch.
Y
N
Y
N
Switch contacts are OK.
See safety circuit trace
(page 31)
Is vent
system
blocked
N
See blower testing
(page 22)
Is blower OK?
Clear blockage
Y
N
Y
N
Correct blower
problem.
Pressure Switch
Slide pressure switch in direction of
arrow while tilting slightly away
from blower housing.
Is vent system length
within vent table
specifications
listed on page 7
Y
Reconfigure vent
system to be
compliant with
vent tables.
N
Y
Pressure switch
wire leads
Page 20
Check tubing and
pressure tap on
switch for blockage.
Is there blockage?
N
Y
Control
Access Cover
Screws
1
2
R
20