TM 5-4520-253-13
Table 4-1. Intermediate Maintenance Troubleshooting – Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
6. HEATER OPERATES NORMALLY BUT AIR FLOW REDUCED.
Check vertical adjustment of fan blades.
Hold or block motor (1 ) and loosen two screws (2). Adjust motor
vertically in motor mount (3) until one-third of depth of fan blades (4)
projects below flange of opening in exchanger housing bottom panel (5).
7.
Make measurement by eye.
HEATER IGNITES BUT RESET CIRCUIT BREAKER REPEATEDLY TRIPS OR HEATER
FAILS TO IGNITE BUT RESET CIRCUIT BREAKER DOES NOT TRIP (FLAME SWITCH
AND BRACKET ASSEMBLY AND RESET CIRCUIT BREAKER GOOD).
Either condition indicates faulty safety shut-down circuit,
Replace PC board. Refer to REMOVE/l INSTALL PC BOARD ASSEMBLY,
page 4-12.
4-10
