TM 5-6115-323-14Section X. MAINTENANCE OF THE CONTROL BOX ASSEMBLY4-24. GeneralThe generator sets, both the AC and DC units,are each equipped with a control box mountedover the generator. They provide a housing forthe components required to control the electricalfunctions of the generator and they provide amounting point for the operator’s controls andinstruments and the power output terminals. Thecontrol boxes are similar in general appearanceand function. However, several of the components,within, differ between the two units. Also, the ACunit control box contains several more compo-nents than is contained in the DC units. Thecomponents within the two control boxes that arethe responsibility of organizational maintenanceare covered separately, for the AC and DC units,by paragraphs in this section.4-25. Control Box Components (AC Unit)a. Test. Test the AC control box components asfollows:(1) Voltmeter.(a) Remove load cables from load terminals.(b) Start the generator set.(c) Position load switch to ON position.(d) With a multimeter, measure the outputvoltage across the load terminals to verify voltageon the set voltmeter. Voltage should not varymore than 5%.(e) If voltage variation exceeds 5%, replacethe voltmeter.(2) Voltage Changeover Switch.(a) With the power off, disconnect the volt-age changeover switch.(b) Position switch on 120 V setting andcheck continuity between the center terminal andthe 120 V terminal.(c) Position switch on 240 V setting andcheck continuity between the center terminal andthe 240 V terminal.(d) If a malfunctioning open circuit is indi-cated on either position, replace the switch.(3) Load Switch.(a) Stop generator set and disconnect termi-nals to load switch.(b) With a multimeter, check the continuityof the load switch. OFF position will indicate anopen circuit; ON position will indicate a shortcircuit.(c) If the above readings are not obtained,replace the load switch.b. Removal. Refer to figure 4-17 and remove thecontrol box components.c. Cleaning and Inspection.(1) Clean all parts thoroughly.(2) Inspect the variable resistor knob forcracks and stripped thread.(3) Inspect the voltmeter and frequency me-ter for signs of burning, broken or cracked glass,water damage, and other damage.(4) Inspect the terminal boards for cracks andburned areas.(5) Inspect the load and voltage changeovertoggle switches for proper operation, signs ofburning, loose wire contacts, stripped threads, andother damage.(6) Inspect the receptacle connector for looseconnections, signs of burning and other damage.(7) Replace all defective parts.d. Installation. Refer to figure 4-17 and installthe control box components.4-26. Control Box Components (DC Unit)a. Test. Test the DC control box components asfollows:(1) Voltmeter.(a) Remove load cables from load terminals.(b) Start the generator set.(c) Position the circuit breaker to the ONposition.(d) With a multimeter, measure the outputvoltage across load terminals to verify the voltageon the set voltmeter. Voltage should not varymore than 4 volts.(e) If voltage variation exceeds 4 volts, thenreplace the voltmeter.(2) Load Meter.,(a) Connect a load of known wattage andproper voltage output terminals of the generatorset. Maximum load is 1500 watts.(b) Start the generator and place circuitbreaker in ON position. Observe the reading onthe set load meter. Meter should indicate accord-ing to the load attached, i.e., 375 watts-25%; 750watts-50%, etc.(c) If the load meter does not read withinspecifications, replace it.4-22Change 1
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