Lang GCCO-T Service Manual page 50

To help troubleshoot the oven you should perform the following "Manual Override" test:
Open drop down door located on the lower right side, directly below front panel.
Turn back up toggle (on/off) switch to "on" position.
Turn main power switch to "on" position.
Check oven for normal operation.
FAILED IGNITION
PROBABLE CAUSE
Defective Power Switch (-PP
only)
Defective Power Switch
output on circuit board
(JP37)
Defective Ignition output
Defective component
transformer
Defective Spark Module
Defective pilot valve
Defective flame sensor
Plugged orifice
IMPORTANT NOTICE: Power must be disconnected at source when disconnecting any ribbon cable or any
connector from CPU or Display. Failure to do so will result in damage to the Display board and CPU.
TROUBLESHOOTING GCCO-PP / -PT
CORRECTIVE ACTION
Confirm that toggle switch is getting correct voltage.
Check power switch for normal operation.
Confirm that JP37 has 5VDC in the off position and nominal voltage
in the on position.
If JP37 has a constant 5VDC check toggle switch for normal
operation.
Check for 24VAC at JP1 to Common (C)
If no voltage is present:
CPU is operating properly.
If voltage is present:
Output has failed.
Confirm that 208/240VAC is feeding primary coil.
Confirm that 24VAC is at secondary coil.
Check for 24VAC at TH.
If no voltage is present:
Check component transformer.
If voltage is present:
Check for pilot ignition.
Replace spark module.
Check for 24VAC at pilot valve.
If no voltage is present:
Check component transformer.
If voltage is Present:
Confirm valve is operational.
Check flame sensor for 12 to 13 micro amps.
Replace flame sensor.
Clean orifice.
50