68. Suppression System Testing
a. Install a battery-powered radio receiver in good operating condition not more than 10 feet from the air compressor.
A wide band receiver covering the frequency range of 0.55 to 156.0 megacycles is preferred.
b. Start the equipment and tune the receiver. Turn receiver volume control to maximum and select three widely
separated frequencies for listening. Use frequencies that are free from signals with strong carriers so that the receiver will
be in its most sensitive operating condition.
c. Operate the engine throttle manually and listen to receiver speaker or headset. A regular clicking sound which
varies with engine speed and ceases the instant the ignition switch is shut off is caused by the ignition circuit.
d. Systematically replace the suppression components in the compressor (par. 69), testing after the replacement of
each component to see if the trouble has been eliminated. Make sure that bonding straps and all electrical components
(voltage regulator, generator, and so forth) are securely attached and mounted.
69. Suppression Component Replacements
a. General. When replacing suppression components, be sure that new components are interconnected and
attached in exactly the same position as the defective material was originally installed.
It is important that toothed lockwashers be used for attaching bonding straps to assure a firm bond.
b. Ignition System Components.
(1) One bond strap is located between voltage regulator ground and generator stud and one bond strap
connects the voltage regulator support to the crankcase upper oil pan.
(2) One bond strap is located between magnetic switch mounting bolt and compressor support frame.
(3) A capacitor is connected between the voltage regulator center terminal and the frame.
c. Instrument panel.
(1) One bond strap is connected between the instrument panel and the top hood of the compressor housing.
(2) Shielded wire connects the ammeter to the voltage regulator.
d. Engine parts.
(1) A bond strap connects each side of the radiator to the compressor support frame.
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