Lang GCCO-T Service Manual page 47

NO MOTOR COMPUTER MODE
PROBABLE CAUSE
No 24 VAC on Interface
board
NO HEAT MANUAL MODE
NOTE: Fan must be operating before trouble shooting No heat.
PROBABLE CAUSE
Pilot burner fails to light
Spark observed
TROUBLESHOOTING GCCO-C CONT'D
CORRECTIVE ACTION
Check for 24 VAC at TP4 to common ("D").
If 24 VAC is not measured:
Confirm that back up relay is energizing.
Replace if defective.
If 24 VAC is measured:
Check for 24 VAC at TP5.
Replace Interface board if defective.
CORRECTIVE ACTION
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 initial 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 for 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.
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