TM 5-4520-253-13
Table 4-1. Intermediate Maintenance Troubleshooting – Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
4. HEATER BACKFIRES.
NOTE
Operation of heater with highly volatile fuels can cause per-
colation of fuel. Popping or backfiring occurs as bubbles
pass through fuel jet. Certain types of gasoline can cause
this. If possible, operate heater with another type of fuel
before proceeding.
Step 1.
Check heat exchanger insulators
behind burner head adapter ring.
Remove burner head assembly to
gain access to insulators. Refer
to REMOVE/l INSTALL BURNER
HEAD ASSEMBLY, page 4-62.
Replace frayed, torn, or
otherwise damaged insula-
tors. Pull out damaged
insulators and insert new
ones. Insulators are flex-
ible and split to facilitate
installation.
Step 2. Check combustion blower motor operation.
If motor appears to run slower than
normal, check brushes, commutator, bearings, and fan assemblies.
Clean motor and replace defective parts. Refer to REPAIR BLOWER
MOTOR, page 4-51.
Step 3. Test blower motor.
Refer to DISASSEMBLE/ASSEMBLE/TEST BLOWER
MOTOR, TESTING, page 4-49.
If blower fails to displace at least 15 inches of water, replace blower
motor.
Refer to REMOVE/l INSTALL COMBUSTION BLOWER AND
HOUSING, page 4-40.
5. HEATER OPERATES NORMALLY BUT HEAT OUTPUT REDUCED
Remove burner head assembly and visually check inside heat exchanger for excessive
carbon buildup. Refer to REMOVE/l INSTALL BURNER HEAD ASSEMBLY, REMOVAL,
page 4-62.
Clean heat exchanger. Refer to CLEAN/l INSPECT/REPAIR HEAT
EXCHANGER, CLEANING, page 4-72.
4-9
