PDX SERVICE PROCEDURE VIII

Safety Circuit Voltage Trace

Safety Circuit Voltage
Trace WARNING
120 volt potential exposure. Use caution
making voltage checks to avoid personal injury.
Position gas control switch to the “ON”
position and adjust thermostat dial to call
for heat, Is there 10 to13 VAC betwee n
red wire leading to blower temperature
switch and green ground wi re?
Blower must be running during this
voltage check.
(see photo 28)
Red wire leading to
blower temp. switch
Green ground wire
28
Yellow wire
leading from
pressure switch
Y
Is there 10 to 13 V AC between yellow
wire leading from pressure switch and
green ground wire?
(see photo 28)
Do you hear or can you
see the igniter sparking?
Y
Y
Is LEDon gas valve flashing
the “heartbeat” code
(alternating bright/dim)
N
Safety circuit
voltage is OK.
No voltage from gas control,
call for technical s upport.
Y

NOTE: This procedureassumes a cool tank.

Verify 120VAC to g as
control (see page 30)
Is there continuity
through blower
temperature switch?
(see page 21)
Y
Check for loose or
broken wire
connection at switch
terminals
N
N
Determine cause of blower
temperature switc h
activation and correct.
Check igniter/senso r
(see page 16)
is igniter/sensor O K?
If burnerdoes not light,
observe LED flash code
on gas valve and refer to
troubleshooting se ction
on page12
N
N
Page 30
27

Step 2. Remove three screws (Phillips Screw driver) from contro l

access cover on blower and remove cover (see photo26).

Faulty cord set or
gas control.
Y
Correct igniter/
sensor problem.
PDX Series
30