Lang GCCO-T Service Manual page 53

NO HEAT, MANUAL MODE
PROBABLE CAUSE
Defective back-up toggle
switch
Defective back-up relay
Defective component
transformer
Failed Ignition
Defective Thermostat
Defective centrifugal switch in
motor
Defective main valve
TROUBLESHOOTING GCCO-PP / -PT CONT'D
CORRECTIVE ACTION
Confirm that toggle switch is in the "ON" position.
Check toggle switch for normal operation.
Check for 120VAC at relay coil.
If no voltage is present:
Confirm that points are making.
If voltage is present:
Replace relay.
Confirm that 120VAC is feeding primary coil.
Confirm that 24VAC is at secondary coil.
See Failed Ignition portion of this manual.
Check for 24VAC at MV on the spark modual to ground.
If no voltage is present:
Confirm that pilot is lit.
Replace as necessary.
If voltage is present:
Check thermostat for normal operation.
Confirm that thermostat has 24VAC.
If no voltage is present
Check component transformer and wiring for normal operation.
If voltage is present
Check thermostat for normal operation. Replace as necessary.
Disconnect centrifugal switch and check of continuity while the
motor is running.
If no continuity is present:
Replace motor.
If continutiy is present:
Check thermostat for normal operation.
Check wires
Check for 24VAC across valve.
If no voltage is present:
Confirm that wires have continuity.
If voltage is present:
Replace valve.
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