29. Periodic Battery Check
Thecondition of the battery should be determined every50 to 100 hours initially. Periodic battery checkintervalsmay be varied as service experience dictates by referringto Battery Service Recordin chapter 5. If the temperatures are above 100°F for an extended period,or if battery problemsarise, the batteryshould be checked more frequently. Thischeck will also equalize the cell voltages.
(a)
Dischargethe battery.
(b)
Rechargebattery.
(c)
Checkthe electrolyte level;adjust if necessary.
(d)
Rest battery for 24 hours.
NOTE: The battery cells must be at room temperature.
(e)
Dischargethe battery at 40 amps; atone hour the battery voltageshould be 20 volts.
(f)
If the battery voltage is below 20 volts, rest battery for 4 hours and repeat steps 2 thru 5.
(g)
Duringthis discharge, checkthe individual cell voltages. If the battery voltageis againbelow 20volts, replace each cell that fell below 1 volt before 1 hour. Consult battery manufacturer's service and repair literature.
30. Cell Voltage Check
Thecell voltage check requires the use of a 0-50 Vdc range voltmeterwith at least 2% accuracy; a digital readout type is suggested.
(a)
Connectthe negative lead of the voltmeter to the negativeterminalof the Elconconnector.
(b)
Withthe positive probe,startingat the positive terminalof cell number 20, measure and record voltagereadingsof all cells in reverse order of numerical sequence(referto Figure 24-10).
(c)
Disconnectthe negative lead of voltmeterfromnegativeterminalof Elcon connector and connectpositivelead of voltmeter to negative terminal of Elcon connector.
(d)
Withthe negative probe,startingat the negative terminal of cell number1, measure and record voltagereadingsof all cells in numeric sequence(refer to Figure24-10).
(e)
Thedefectivecell may be found by monitoring the voltage readingsobtainedbetweeneach cell terminaland the batterycase. The lowest voltages will occurat the terminal connectorson eachside of the defective cell. Replace defectivecell.
EFFECTIVITY:
040-999 24-30PAGE23
24-30-00 Jan 10/90
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. DC Generation (continued)
31. BatteryCleaning
WARNING: DO NOT CLEAN BATTERYWITH CHEMICAL OR PETROLEUM BASELIQUIDS. DO NOT USE SOLVENTS OF ANY KIND.
Nickelcadmiumbatteriesmust be kept clean to maintain an airworthy condition. Contamination cancause conductive paths leading to self-discharge.The battery shouldbe cleaned and serviced every100 operating hoursor 60 days, whichever occursfirst. Charge ratesdeterminewater consumption,thus operating conditionsmustdetermineservicefrequency. Nicad batteries should neverbe serviced in a lead acid battery service area. Even small traces of sulfuric acid entering a nicad battery can cause permanent damage.
(a)
Wipedown all surfaces with a clean dry cloth.
(b)
Loosenstubborn deposits with a plastic scraperand using filtered dry low pressureair, with a nonmetallicnozzle,blowaway contamination (dust, salts, etc) from aroundthe tops of the cells and case. Use eye protection.
EFFECTIVITY:
040-999
Jan10/9024-30-00
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
B. OverheadMeterandSwitchPanelAssembly
Theoverheadmeterandswitchpanelassemblycontainsfourremovableswitchpanelsmadeof electroluminescent
plastic,threebezelmountedelectricalgauges,a seat beltlightswitch,adomelight switch,a no smokinglightswitch,andawindshieldwipercontrolswitch.
Theswitchesare locatedon the electroluminescentpanelsin royalite trim panels. They arelocated centrallyabovethe windshieldandon the cockpitceiling. The switchesareof the rockertype.
1. Removalof Engine ControlPanelSwitch
(a)
Removescrewssecuringcoverpanelto switchpanel. Removecoverpanel.
(b)
Removescrewssecuringswitchto panel assembly.
(c)
Removewire connector fromswitch.
2. Installationof EngineControlPanelSwitch
(a)Attachwireconnectorto switch.
(b)
Placeswitchin panelassembly.Securewithtwo screws.
(c)
Placecoverpanelon switch panel.Securewith screws.
3. Removalof RockerSwitch
(a)
Removefour screwssecuringfacepanel. Pullpanelawayfrom panelassembly.
(b)
Removewiresfromterminalson backof switch.
NOTE:To facilitate installation,mark wires andlocationon switch.
(c)
Removeswitchfromfacepanel.
4. Installationof Rocker Switch
(a)
Positionswitchin face paneland press intoplace.
(b)
Connectwiresto terminals onrearofswitch.
(c)
Positionfacepanelon panel assembly.Securewithscrewspreviouslyremoved.
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