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PDX SERVICE PROCEDURE III
Pressure Switch Testing and
Replacement
Inlet Pressure Switch
Testing
WARNING
120 volt potential exposure. Use caution
making voltage checks to avoid personal injury.
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 7).
Step 3. Remove wires from inlet pressure switch.
Use a multi-meter set to the
ohms setting. With blower off,
check across pressure
switch terminals.
Are switch contacts closed?
Check tubing and pressure
tap on switch for blockage.
Is there blockage?
Replace switch
(see page 20)
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
remain closed with blower
running with the switch in
the vertical postition?
With steps 1,2 & 3
complete.
Y
N
Y
N
Switch contacts are OK.
See exhaust pressure
switch testing (page 17)
Is vent
system
blocked
N
See blower testing
(page 21)
Is blower OK?
Clear blockage
Y
N
Y
N
Correct blower
problem.
Is vent system length
within vent table
specifications
listed on page 7
Y
Reconfigure vent
system to be
compliant with
vent tables.
N
Y
Page 19
Check tubing and
pressure tap on
switch for blockage.
Is there blockage?
N
Y
PDX Series
7
Exhaust
pressure switch
Inlet pressure
switch
Inlet pressure
switch wire
leads (found
inside cover)
19