PDX SERVICE PROCEDURE III

Pressure Switch Testing and

Replacement

Exhaust 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” posit ion.

Step 2. Remove the three screws (Phillips screw driver) from control access cover on blower assembly and

remove cover (see photo 1).

Step 3. Remove tubing and wires from inlet pressure switch.

Step 4. Carefully remove pressure switch from blower housing (see photo 2)

2
Use a multi-meter set to the
ohms setting. With b lower off,
check across pressure
switch terminals.
Are switchcontacts open?
(no electricalcontinuity)
Check tubing and p ressure
tap on switch for blockage.
Is there blockage?
Replace switch
(see page 18)
Position gas valve pow er
switch to the “ON” position
and adjust thermostat
to call for heat,
this will start the blo wer.
Checkwith multi-meter, do
pressure switch cont acts
close withblower running
with the switch in the
vertical postition?
With steps 1,2,3 & 4
complete,
disconnect wire le ads from
pressure switch.
Y
N
Y
N
Switch contacts areOK.
See safety circuit trace
(page 30)
Is vent
system
blocked
NSee blower testing
(page 21)
Is blower OK?
Clear blockage
Y
N
Y
N
Correct blower
problem.
Pressure Switch
Slide pressure swit ch in direction
of arrow while tilti ng slightly away
from blower housing.
Is vent system length
within vent table
specifications
listed on page7
Y
Reconfigure vent
system tobe
compliant with
vent tables.
N
Y
Pressure switch
wire leads
Page 17
Check tubing and
pressure tap on
switch for blockage.
Is there blockage?
N
Y
PDX Series
1
Exhaust
pressure switch
Inlet pressure
switch
17