TM 5-4520-241-14
Table 4-2. Organizational Maintenance Troubleshooting - Continued
MALFUNCTION
TESTING OR INSPECTION
CORRECTIVE ACTION
4 - Continued
CAUTION
When checking spark, do not allow spark gap to exceed 1/8 inch. Greater gap will
cause excessively high potential buildup resulting in insulation breakdown either
internally or in the ignition cable.
Step 10. Check for ignition spark. Remove igniter from burner head, but make sure igniter is tightly
connected to ignition cable. Clamp igniter body against a heater case ground. Connect power
plug, check that room thermostat is set above ambient temperature, and turn on heater.
If no spark is visible at igniter tip, check per step 11. If spark is visible, check per step 12.
Step 11. Check for power to ignition transformer. Under conditions in step 10, 120 VAC should be present to
white and brown leads of ignition transformer.
If no power is present, check wiring to terminal strip. Replace broken wires or tighten loose
connections. If power is present, ignition transformer is defective. Turn off power and disconnect
power plug. Disconnect white and brown leads from transformer to terminal strip, and ignition
cable at transformer output. Remove screws and washers securing transformer to heater case,
and install new transformer by reversing removal process.
Step 12. Check flame switch. Disconnect power plug and thermostat plug. Open access doors. When heat
exchanger is cool, there must be continuity from the brown wire to the green and the white/black
wires. When the heat exchanger is hot, there must be continuity from the brown wire to the orange
wire and the blue wire. If flame switch is good, check fuel system per steps 13 and following. If
flame switch is bad, replace as follows:
4-26
