TM 9-2350-230-12
TABLE 8-4. TROUBLESHOOTING - CONTINUED
Malfunction
Probable cause
Corrective action
SIGHTING AND FIRE-CONTROL
INSTRUMENTS - CONTINUED
PERISCOPE M47 AND M48
146. Wiper motor does
a. Defective switch
a. Replace switch (fig. 9-101).
not operate.
b.
Faulty wiring or connections.
b. Repair or replace faulty
components.
147. No cleaning fluid
a.
No fluid in reservoir
a. Refill reservoir (fig. 11-37).
from washer
assembly
b.
Faulty pump
b.
Replace pump.
c.
Clogged tubing
c.
Clean tubing or nozzle.
d.
Clogged check valve
d.
Clean check valve.
e.
Loose tubing connection or
e.
Replace defective tubing
leaking tubing
or connectors.
148. Periscope loose
a. Faulty catches
a. Notify support maintenance.
after installation.
b. Loose mount assembly
b. Tighten bolts (fig. 11-36).
c. Worn seal
c. Replace seal (fig. 11-36).
149. No infrared vision
Improper electrical ground
Clean all mating ground
surfaces between mount,
hatch, body and head.
TABLE 8-5. OHMMETER METHOD OF ELECTRICAL TROUBLESHOOTING
a. General. The ohmmeter method of electrical
the meter. All electrical circuits have some resistance.
troubleshooting (fig. 8-2) uses continuity tests to
Resistances may be so low, or' high, they cannot be read
determine whether circuit or device being tested has a
with an ordinary ohmmeter. An ohmmeter with a full-
continuous electrical path through cables and unit
scale reading of 10 ohms is desirable for measuring low
connected between two test points. An ohmmeter
resistances. Higher range ohmmeters are better suited
indicates, on a calibrated scale, resistance of circuit
for testing insulation leaks. If the normal resistance of
being tested and is equipped with a power source
circuit to be tested is known, select an ohmmeter with a
(battery or hand generator), usually installed inside case
full-scale range higher than normal resistance.
which houses
8-45
