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START
YES
NO
G776 IGNITION CONTROL TROUBLESHOOTING
No spark and system will not work
.
1993 Johnson Controls, Inc. Reprinted with permission.
Is 24VAC
between THS 2
and ground?
Check the following:
1) 120VAC Supply
2) Transformer
3) Thermostat
Open thermostat contacts for
30 seconds. Close contacts
and wait 2 seconds longer
than prepurge (17 sec. total).
Is spark
present now?
System was is lockout. Determine the Cause:
1) Flameout cycling.
2) Internal malfunction.
3) Flame present when it should not be.
Did pilot remain
lit from previous
cycle?
Replace gas
valve.
Turn OFF
supply voltage
Is high voltage
cable securely
connected to spark
transformer?
Connect securely
then turn ON
supply voltage.
Is high voltage
cable brittle, burnt
or cracked?
Replace cable.
Is spark electrode
ceramic cracked?
Replace pilot
burner.
Is spark gap 0.1
inch and located in
pilot gas stream?
Correct or replace
pilot burner. Turn
ON supply voltage.
END
Replace
control.
YES
YES
NO
NO
NO
YES
NO
YES
NO
YES
NO
YES
FIGURE 45
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