Lang GCCO-T Service Manual page 41

NO MOTOR
PROBABLE CAUSE
Defective power switch
Defective Transformer
Gas supply turned off
Defective Pilot
Spark observed
No spark observed
TROUBLESHOOTING GCCO-SII
CORRECTIVE ACTION
Check power switch for normal operation. Replace as necessary.
Check Transformer for normal operation.
Turn gas supply on and check for proper gas pressure. 5" water
column for natural gas and 10" water column for propane.
Perform the following "trial ignition" and look and listen for spark:
Attempt to light the pilot burner. If the burner does not ignite
after 30 seconds, cycle power and repeat "trial ignition". The
pilot may require several trials for ignition to bleed air from the
gas piping. After the ignition attempt, pilot should only require
2-5 seconds for normal start-up.
Check for 24 VAC at pilot valve.
If 24 VAC is measured, turn oven off:
Check for pilot burner orifice blockage. Clean and repair as
necessary.
Perform trial ignition, as described in above section.
Replace gas valve.
If 24 VAC is not measured:
Check for 24 VAC at PV on spark module.
Check continuity on wire between PV on spark module and Pilot
Valve.
Turn oven on. Refer to wiring diagram and check for 24 VAC at the TH
terminal on the spark module.
If 24 VAC is measured. Turn oven off:
Check large orange wire from ignitor module to pilot burner for
continuity, and for insulation breaks.
Replace wire as necessary.
Check spark electrode and hood of pilot burner.
Check spark gap. Clean and regap if necessary.
Check pilot burner for any evidence of moisture. Dry pilot if
necessary.
Replace spark module if above checks do not correct problem.
If 24 VAC is not measured. Turn oven off:
Check 120/24 VAC trasformer for 18.9 Ω on the primary coil and 1
Ωon the secondary coil.
Turn unit back on and check primary coil for 120 VAC and secondary
for 24 VAC.
Replace transformer.
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