Condensing PDV Series
18
Service Procedure III
Pressure Switch Testing and
Replacement
Pressure Switch Testing & Replacement
Step 1. Position the power switch on the gas
control to the “OFF” position.
Step 2. Remove the three screws (Phillips screwdriver) from the control access
cover on the blower assembly and remove the cover. Do not disconnect the
blower harness from the cover (see photo 1).
Step 3. Remove the 2 screws (Phillips screwdriver) and carefully remove the
pressure switch to gain access to the wire lead connections (see photo 2).
co
With steps 1,2 & 3
complete, disconnect wire
leads from either the intake
or exhaust pressure switch.
Use a mutli-meter set to the ohms
setting. With blower turned off, check
across pressure switch terminals.
Are switch contacts open?
(no electrical continuity)
N
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 the pressure
switch contacts close with blower
running?
Y
N
Y
Check tubing and
pressure tap on
switch for blockage.
Is there blockage?
Check tubing and pressure
tap on switch for blockage.
Is there blockage?
Switch contacts are OK.
See Safety Circuit Voltage
Trace (page 29).
Y
N
Replace switch
(see page 17).
N
N
Remove 3 Phillips screws to
remove cover.
Remove 2 Phillips screws to
pressure switch.
Clear blockage.
Is vent system
blocked?
Reconfigure vent
system to be compliant
with vent tables.
Correct blower
problem.
Y
Is vent system length
within vent table
specifications listed on
pages 7 & 8?
See blower testing
(page 20)
Is blower OK?
N
N
Y
Y
1
2
Pressure switch wire leads.
Exhaust
WARNING
115 volt potential exposure. Use
caution to avoid personal injury.
Intake
Use a mutli-meter set to the ohms
setting. With blower turned off, check
across pressure switch terminals.
Are switch contacts closed?
(electrical continuity)
N
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 the pressure
switch contacts remain closed
with blower running?
Y
N
Y
Switch contacts
are OK.
See Safety
Circuit Voltage
Trace (page 29).
Refer to “Check
tubing and pressure
tap…” box in flow
chart.
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