TM 5-4520-256-14
3-9. TROUBLESHOOTING - Continued.
Table 3-2. Unit Troubleshooting - continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
2.
SAFETY RELEASE INDICATOR LIGHT IS ILLUMINATED AND AUDIBLE ALARM IS SOUNDING - Continued.
Step 7.
With switch (S1) set to HEAT mode, observe through sightglass for flame.
If audible alarm sounds, set (S1) to VENT, wait approximately 60 seconds, reset combustion control relay
K8 and set (S1) to HEAT mode. Check for flame within 10 seconds.
If audible alarm sounds immediately, proceed to step 8.
If flame is not present, clean or replace fuel nozzle as needed (para 3-39). If flame is visible and audible
alarm sounds after 10 seconds, proceed to step 8.
Step 8.
Inspect flame detector (para 3-37). If malfunction still exists, proceed to step 9.
Step 9.
Inspect high temperature safety thermostat (para 3-27).
If malfunction still exists, replace combustion control relay K8.
3.
FUEL PRESSURE FAILS TO RISE (HEAT MODE).
Step 1.
Check that INTERNAL TANK/EXTERNAL TANK selector switch is set for proper tank being used. If
switch is improperly set, correctly set switch.
If switch is properly set, proceed to step 2.
Step 2.
With OFF/VENT/HEAT switch (S1) set to VENT mode check that fan is operating. If fan fails to
operate, proceed to MALFUNCTION 1.
If fan is operating, proceed to step 3.
Step 3.
With (S1) in VENT mode, check that the fuel system is properly purged of air (para 1-13b).
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