d. Test Procedure.
(1) Energize power supply and adjust to read 20
volts on V1, Open valve to the fuel supply.
(2) Leave switch B in the off position (LO), and
turn switch A. Make the following observations during
(a) Ignition time. Ignition of this heater maybe
inaudible when burning diesel fuel. Ignition must oc-
cur within 75 seconds maximum. If exact ignition time
cannot be determined, flame detector switch crossover
(indicated by pilot lamp lighting up) must be the deter-
mining factor. Flame detector switch must light pilot
lamp within 105 seconds.
(b) Electric current as measured by ammeter
must be 12.5 amperes or less.
The fuel control valve contains a fuel heater
which may be energized in ambients below
70° F, drawing an extra 3.5 to 4.7 amperes. If
this occurs, disconnect the thermostat lead
(No, 3 from the fuel control valve) from the
terminal strip on the heater and retest,
(3) Immediately after flame detector switch trips,
turn on switch B (heater on HI). Adjust power supply
to read 24 volts on voltmeter V1, and observe the am-
meter during running cycle. Electric current must be
10.5 amperes maximum.
(4) Let heater run for two minutes, and inspect ex-
haust. No smoke should be visible.
TM 9-23 50-256-34-1
Visible smoke after two minutes of operation
is not acceptable. Check for low voltage, a
slow-running motor, or improperly calibrated
fuel control valve. Some visible white smoke
is normal until the flame detector switch
(5) Restrict air flow into the ventilating air blower
until the overheat switch opens. Read the temperature
of the switch on the thermometer. Overheat cutout
temperature must be 350° to 500° F.
(6) Remove ventilating air restriction. Heater
should resume burning without requiring a return to
the start cycle.
(7) Adjust power supply to read 30 volts on volt-
meter V1 and turn off switch B. Allow heater to run
for at least one minute. It must continue to burn
(8) Adjust power supply to read 24 volts on volt-
meter V, and turn off switch A to shut off heater. Ob-
serve the time required for blower to shut off. Purge
time must be between 80 and 150 seconds.
(9) If heater does not meet specifications, repair
(10) Shut off power supply and fuel. Allow heater
to cool to a temperature at which it is easy to handle.
Disconnect the fuel and electrical connections and re-
move the pyrometer duct. Remove heater from test
Paragraphs 3-37 through 3-41.