TM 5-4520-240-14
Table 4-2. Organizationol Maintenance Troubleshooting-Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
CAUTION
When checking spark, do not allow spark gap to exceed 1/8 inch. Greater gap will cause ex-
cessively high potential buildup resulting in insulation breakdown either internally or in the
ignition cable.
Step 2. Remove ignition cable from igniter and position cable so that cable end is 1/8 inch from a grounded surface. Turn power on.
If spark is weak or intermittent report to direct support maintenance.
Step 3. Remove igniter and check for damage.
Replace a damaged igniter (para 4-30).
Step 4. Check exhaust system for obstructions.
Remove exhaust obstructions.
Step 5. Check that exhaust piping is installed as shown in figure 4-1.
Revise exhaust piping to conform to requirements listed in paragraph 4-3.
6. HEATER CYCLES ON AND OFF EXCESSIVELY.
Step 1. Check that room thermostat is installed as described in paragraph 4-3.
Relocate improperly installed thermostat as specified in paragraph 4-3.
Step 2. Disconnect thermostat power cable from thermostat. Use a multimeter set to read 1X resistance and check continuity across
thermostat contacts while operating thermostat temperature control. Continuity must be made sharply as temperature control
is moved up to and past ambient temperature. Continuity must be broken sharply as temperature control is moved down to and
past ambient temperature.
Replace thermostat if contact operation is intermittent or erratic (para 4-3).
7. HEATER SMOKES.
Step 1. Check that fuel adjustment is correct.
Adjust fuel adjustment needle (para 4-23a).
Step 2. Check that combustion air inlet is not blocked or dirty.
Clean or repair combustion air inlet or replace damaged parts (para 4-18).
Step 3. Remove side cover panel and check that combustion air hose is not tom or restricted.
Replace a damaged combustion air hose (para 4-30).
Step 4. Check that carburetor float bowl controls fuel flow. With the heater energized and the fuel pump running, remove the slotted
plug from the top side of the fuel bowl. No fuel should flow through opening.
Replace a defective carburetor (para 4-23).
Section VI. RADIO INTERFERENCE SUPPRESSION
4-12. General Methods Used to Attain
4-13. Primary Interference Suppression
Proper Suppression.
Components.
a. A 0.47 microfarad, 200 vdc capacitor (1, fig. 4-3) is
Essentially, suppression is attained by providing a low
resistance path to ground for stray currents. The
installed on the blower motor at the motor terminal.
methods used include shielding the ignition wires, in-
This capacitor suppresses the radio frequency inter-
ference generated by the arcing of the brushes at the
stalling a capacitor on the blower motor, and installa-
tion of an rf filter in the ignition power supply.
motor commutator.
4-6