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PDX Series
Pressure Switch Testing
Step 1.
Position power switch on gas control
to the "OFF" position.
Step 2.
Remove the three screws (Phillips screw driver) from control access cover on blower assembly and
remove cover (see photo 1).
Step 3.
Carefully remove pressure switch from blower housing (see photo 2)
With steps 1,2 & 3 complete,
disconnect wire leads from
pressure switch.
Use a multi-meter set to the
ohms setting. With blower off,
check across pressure
switch terminals.
Are switch contacts open?
(no electrical continuity)
Y
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 the
switch in the vertical
postition?
Y
Switch contacts are OK.
See safety circuit trace
(page 30)
18
Exhaust pressure
switch
Pressure switch
wire leads
``
N
Y
Check tubing and
N
pressure tap on
switch for blockage.
Is there blockage?
PDX SERVICE PROCEDURE III
Pressure Switch Testing and
120 volt potential exposure. Use caution
making voltage checks to avoid personal injury.
1
Slide pressure switch in direction of
3
arrow while tilting slightly away
from blower housing.
Check tubing and pressure tap
N
on switch for blockage.
Is there blockage?
Y
Clear blockage
Y
Is vent system length
Is vent
N
N
system
blocked
listed on page 7 or 8
Replacement
WARNING
2
Replace switch
(see page 18)
See blower testing
within vent table
Y
specifications
Is blower OK?
N
Reconfigure vent
Correct blower
system to be
compliant with
vent tables.
Pressure Switch
Y
(page 21)
N
problem.
Page 18
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