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UPV75 Service Procedure IX – Safety Circuit Voltage Trace
Safety Circuit Voltage Trace
NOTE:
This procedure assumes a cool tank.
Remove three screws (T20 Torx screwdriver) from control
access cover on blower and remove cover (see photo 20).
WARNING
115 volt potential exposure.
Use caution to avoid personal injury.
Position gas control switch on the “ON” position
and adjust thermostat dial to call for heat. Is
there 10 to 13 VAC between switch and jacket
head screw shown in photo 21? Blower must
be running during this voltage check.
Is LED on gas valve
flashing the “heartbeat”
code (alternating
bright/dim).
No voltage from gas control,
call Technical Support.
Verify 115VAC to gas
control (see page 30).
Is there 10 to 13 VAC between
red wire on temp switch and
jacket head screw?
Is there continuity through blower
temperature switch? (see page 24).
Check for loose or
broken wire connection
at switch terminals.
Determine case of blower
temperature switch
activation and correct.
Do you hear or
can you see the
igniter sparking?
Check igniter/sensor
(see page 15).
Is igniter/sensor OK?
Safety circuit
voltage is OK.
If burner does not light, observe LED
flash code on gas valve and refer to
troubleshooting section on page 12.
Correct igniter/sensor problem.
Faulty cord set or gas control.
Y
Y
Y
Y
Y
Y
N
N
N
N
N
N
20
21
Blue wire leading to
blower temp. switch
Red wire leading from
pressure switch
Jacket head screw
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