TM 5-4520-240-14
Section X. MAINTENANCE OF BURNER ASSEMBLY
4-29. Description.
burner head.
b. Cleaning and Inspection.
a. Air Inlet Hose. On Model UH-48-C, the air inlet
hose is a spring-wound, neoprene-coated tube. On
WARNING
Model UH-48-D, the air inlet hose is a paper-
Clean parts in a well-ventilated area.
aluminum-paper laminated tube. The air inlet hose
Avoid inhalation of solvent fumes and
conducts combustion air from the combustion air inlet
prolonged exposure of skin to cleaning
on the burner head.
solvent. Wash exposed skin
b. Igniter. The igniter is similar to an automotive
thoroughly. Dry cleaning solvent (fed.
spark plug, and it performs a similar function. High
spec. P-D-680) used to clean parts is
voltage from the ignition power supply creates a spark
potentially dangerous to personnel
between the igniter electrode and the grounded igniter
and property. Do not use near open
sleeve that surrounds the electrode. It is this spark
flame or excessive heat. Flash point of
which ignites the fuel and air mixture in the burner
solvent is 100F (38C).
head.
(1) Clean the igniter, the glow plug, and the outside
c. Glow Plug. The glow plug is energized only while
of the burner head with dry cleaning solvent (fed. spec.
the heater is being started. The glow plug is a wire
P-D-680). Do not immerse the glow plug in solvent or
wound electrical heater that preheats the burner head
allow solvent to enter the burner head, Allow all parts
to ensure vaporization of the fuel for rapid ignition.
to dry thoroughly before installation.
d. Burner Head. The burner head provides mounting
(2) Inspect the electrode and outer shell of the ig-
for the carburetor, igniter, and glow plug, and contains
niter for burning or pitting. Inspect ceramic parts for
a small combustion chamber, Air from the combustion
cracks or breaks. Inspect threads for damage. Replace
air blower enters the burner head through the combus-
a damaged igniter.
tion air hose, and mixes with the fuel metered by the
(3) Inspect the glow plug for cracks, frayed insula-
carburetor. Spark from the igniter ignites the fuel and
tion, loose or broken leads, defective element winding,
air mixture inside the burner head, The burning gases
and other damage. Apply 28 vdc across the glow plug
pass through the heat exchanger, which heats ventila-
leads and check that the glow plug heats. Replace a
tion air flowing around it, and exit the heater through
damaged or defective glow plug.
the exhaust pipe.
(4) Clean the combustion air hose by shaking it or
blowing through it with compressed air. Replace the
4-30. Igniter, Glow Plug, and Combustion
hose if it is tom, deteriorated, restricted, or damaged.
Air Hose.
(5) Inspect the ignition cable for cracks, deteriora-
a. Removal.
tion, fraying, and other damage. Report a defective ca-
WARNING
ble to direct support maintenance,
The ignition system of this space
(6) Report a damaged or defective burner head to
heater contains dangerous voltages
direct support maintenance for repair.
which can cause severe electrical
(7) Discard and replace the gaskets,
shock. Be sure to disconnect the power
c. Installation.
plug before repairing the heater.
(1) Install the glow plug (8, fig. 4-13) and igniter (4)
(1) Disconnect the power plug and remove the top
in the burner head, using new gaskets (5 and 9). Con-
and side cover panels to provide access to the burner
nect the blue glow plug lead using nut (6) and lock
head.
washer (7). Insert the waterproof connector (3) on the
(2) Loosen the two clamps (1, fig. 4-13) securing the
ignition cable and connect the ignition cable to the ig-
combustion air hose (2) to the combustion air blower
niter.
outlet and the burner head. Remove the combustion air
hose, and remove the clamps from the hose.
(2) Slide the clamps (1) over the ends of the combus-
(3) Unscrew the nut on the ignition cable (4, fig.
tion air hose (2), and fit the hose over the combustion
4-7) and remove the cable and the waterproof connector
air blower outlet and the burner head air inlet. Tighten
(3, fig. 4-13). Unscrew the igniter (4) and remove the ig-
the clamps.
niter and the gasket (5) from the burner head.
(3) Reinstall the top and side cover panels, connect
(4) Remove the nut (6) and lock washer (7) and dis-
the power plug, and test the heater operation.
connect the blue lead from the glow plug (8). Unscrew
and remove the glow plug and the gasket (9) from the
4-23/(4-24 blank)
Change 1
