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Ignition
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Maintenance Practices
1. General
The maintenance practices in this Section tell you how to remove/install the ignition switch. Refer to the Lycoming Maintenance Manual and the equipment manufacturer's manuals for more data on the engine ignition system.
2. Remove/Install the Ignition Switch
A. Remove the Ignition Switch
Detail Steps/Work Items  Key Items/References 
WARNING: DO NOT WORK ON THE IGNITION SYSTEM UNTIL YOU HAVE MADE IT SAFE BY DISCONNECTING THE SPARK PLUGS. THE PROPELLER CAN TURN SUDDENLY AND CAUSE INJURY TO PERSONS. 
(1)  Make sure that the engine is safe: S The ignition switch is set to OFF. S The throttle is set to IDLE. S The mixture control is set to LEAN CUT-OFF. 
(2)  Remove the engine cowlings.  Refer to Section 71-10. 
(3)  Disconnect the battery.  Refer to Section 24-31. 
(4)  Disconnect the spark plug cables from the spark plugs. 
(5)  Remove the instrument panel cover.  Refer to Section 31-10. So that you can work at the rear of the ignition switch. 
(6)  Remove the four pan-head screws which attach the switch-mounting-plate to the back of the instrument panel.  Hold the ignition switch and mounting plate! 
(7)  Disconnect the electrical cables from the ignition switch.  Make a note of the cable connections. 
(8)  Remove the switch and mounting plate from the airplane. 

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AIRCRAFT AMM
Knurled Ring
Mounting Plate
Spacer
Ignition Switch
% Figure 2: Ignition Switch Installation in Larger Instrument Panels
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B. Install the Ignition Switch
DA 40 Series

Detail Steps/Work Items  Key Items/References 
(1)  Make sure that the spark plug cables are disconnected from the spark plugs. 
(2)  Make sure that the battery is disconnected. 
(3)  If necessary, install the switch in the switch mounting plate: S Move the switch into position in the mounting plate. S Install the knurled ring on the front of the switch to hold the switch in position in the mounting plate.  Make sure that the switch is correctly aligned! 
(4)  Move the mounting plate and switch into position behind the instrument panel.  So that you can connect the cables. 
(5)  Connect the electrical cables to the ignition switch.  Refer to Chapter 92 for the Wiring Diagrams. 
(6)  Move the switch and mounting plate into position in the instrument panel. 
(7)  Install the four pan-head screws which attach the mounting plate to the instrument panel. 

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%

% % % % Figure 3: Ignition Switch Installation in Smaller Instrument Panels %
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%

DA 40 Series

Detail Steps/Work Items  Key Items/References 
(8)  Do a test for correct operation of the ignition switch: S Disconnect the instrument panel connector at the rear of the instrument panel. S Set the ignition switch to OFF. S Set the ignition switch to R. S Set the ignition switch to L. S Set the ignition switch to BOTH. S Set the ignition switch to START. S Set the ignition switch to OFF. S Reconnect the instrument panel connector at the rear of the panel.  Do a resistance test between each switch cable and ground for each switch setting. Connector 2410. Refer to Chapter 92 for the wiring diagrams. Both ignition switch cables zero ohms. Left zero ohms, right M ohms. Left M ohms, right zero ohms. Both cables M ohms. Both cables M ohms. 
　
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