Lang GCCO-T, Service Manual, Page: 44 / 73

44
TROUBLESHOOTING GCCO-C CONT’D
PROBABLE CAUSE CORRECTIVE ACTION
No spark observed Turn one 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 igniter 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 re-gap 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 transformer for 18.9
Ω
on the primary coil and 1
Ω
on the secondary coil.
Turn unit back on and check primary coil for 120 VAC and secondary
for 24 VAC.
Replace transformer.
Igniter continues to spark
after pilot is lit Check pilot for strong flame and good contact with sensor.
Check sense wire for 12 to 13 micro amps on spark module. (Johnson
Control spark modules use “#4” terminal and Channel spark modules
use “Sense” terminal).
Turn oven off and check sense wire for continuity.
Replace sense wire or spark module as necessary.
Defective back-up relay
Check relay for normal operation (on GCCO ovens relay will be
energized in computer mode).
Check coil for 24 VAC.
If 24 VAC is measured. Turn oven off and:
Check coil for 80
Ω
.
Replace if necessary.
If 24 VAC is not measured.
Verify that back up switch is in “off” position.
Check back-up switch for normal operation. (DPDT)
Check any wires for short.