18
UPV75 Service Procedure III – Pressure Switch Testing and
Replacement
Pressure Switch Testing
Step 1. Position power switch on gas control to the
“OFF” position.
Step 2. Remove the three screws (T20 Torx 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).
WARNING
115 volt potential exposure.
Use caution to avoid personal injury.
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)
Position gas valve
power switch to
the “ON” position
and adjust
thermostat to call
for heat, this will
start the blower.
Check with the
multi-meter, do
pressure switch
contacts close
with the blower
running?
Switch contacts are
OK. See safety circuit
trace (page 30).
Check tubing and pressure
tap on switch for blockage.
Is there blockage?
Replace switch
(see page 19).
Reconfigure vent
system to be compliant
with vent tables.
Correct blower
problem.
Clear blockage.
Check
tubing and
pressure
tap on
switch for
blockage. Is
there
blockage?
Is vent system
blocked?
Slide pressure switch in direction
of arrow while tilting slightly away
from blower housing.
Pressure
switch wire
leads
1
2
Is vent system length
within vent table
specifications listed on
page 7.
See blower testing
(page 20)
Is blower OK?
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
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