Johnson Controls G77 Series Installation Sheets Manual page 17

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Start
Is 24 VAC
present between
Terminal 2 and
ground?
Yes
Open thermostat contacts for
30 seconds and then close
Is
Yes
spark present
now?
No
Did
pilot remain lit Yes
from previous
cycle?
No
Turn off
supply voltage
gap per manufacturer's
Figure 12: No Spark, and System Does Not Work
GG77x Intermittent Pilot Ignition Controls Technical Bulletin
No
Check for defective transformer,
thermostat, or faulty wiring
System was in lockout, causes
include flameout or an internal fault
Replace
gas valve
Is spark
cable securely
No
connected to ignition
control?
Yes
Is
Yes
spark cable
Replace
brittle, burnt, or
cable
cracked?
No
Is spark
Yes
Replace pilot
electrode ceramic
cracked?
No
Is spark
No
specifications and
located in pilot gas
stream?
Yes
Replace
control
Correct
burner
Correct or
replace pilot
burner
End
17