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3-15. Foam Does Not Have Proper Characteristics
for Effective- Use
Probable cause
Possible remedy
Improperly adjusted
foam proportion regu-
lating valve ................ Adjust foam metering
valve. (pare 2-13)
Improper nozzle Change nozzle.
Foam concentrate liquid -
supply is diluted or
contaminated ............ Drain and flush foam sys-
tem. Fill with concentrate
of proper quality. (pare
2-13)
3-16. Hose Reel Assemblies Stick and Bind When
Reeling or Unreeling Hose
Probable cause
Possible remedy
Insufficient lubrication
of hose reel shaft
bearings.................... Lubricate as specified in
LO 5-4210-213-12.
Hose reel assemblies
damaged or defective.....Replace hose reel. (pare
3-88)
3-17. Hose Reel Assemblies Inoperative
Probable cause
Possible remedy
Motor solenoid relay
defective.................... Replace relay (pare 3-88)
Probable cause
Possible remedy
Hose reel switch
defective.................... Replace switch (pare 3-67)
Hose-reel assemblies
damaged or defective.. Replace hose reel (pare
3-88)
3-18.: Siren Inoperative
Probable cause
Possible remedy
Wiring defective ............ Tighten loose connections
and replace wiring as
necessary (pare -49)
Siren hand switch
defective.................... Replace defective hand
switch (pare 3-50)
Defective siren .............. Replace or repair defective
siren (pare 3-50)
3-19. Spotlight or Warning lights Inoperative
Probable cause
Possible remedy
Wiring defective Tighten loose connections
and replace wiring as
necessary (pare 3-49)
Warning light switch
defective.................... Replace defective warning
light switch (pare 3-68)
Rear ILO spotlight......... Replace defective rear ILO
spotlight (pare 3-78)
Warning light defective . Replace or repair defective
warning light (pare 3-52)
Spotlight defective ........ Replace defective spotlight
(para 3-51).
Section VI. RADIO-INTERFERENCE SUPPRESSION
3-20. Definitions
a.
Interference. The term "interference" as used
herein applies to electrical disturbances in the radio
frequency range which are generated by the fire truck
and which may interfere with the proper operation of
radio receivers or other electronic equipment, or enable
the enemy to locate the equipment.
b.
Interference
Suppression.
The
term
"interference suppression" as used herein applies to the
methods used to eliminate or effectively reduce radio
interference generated by the fire truck.
3-21. General Methods Used to Attain Proper
Suppression:
Essentially, suppression is attained by providing a low
resistance and high-frequency wires, grounding the
frame with bonding straps, and using capacitors and
resistors.
3-22. Interference Suppression Components
a.
Primary Suppression Components.
(1)
Capacitors. The fire truck has four
capacitors located on the siren, siren flasher, and
warning light. The capacitors are illustrated on figure 3
4.
(2)
Ground Strap. The unit has four ground
straps, two from chassis to frame and one each located
on the frame to hose motor assemblies. The ground
straps are illustrated on figure 3-4
b.
Secondary - Suppression Components. Tooth-
type lockwashers are used to assure good metal-to-
metal
contact
where
electrical
components
are
mounted.
3-23. Replacement of Suppression Components
Primary Suppression Components. Replace radio
interference components with new components that are
identical. Capacitors must be
3-10
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