PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

B. Maintenance Practices (continued)
11. Deicer Boots (continued)
ViewA  ViewB 
DeicerPowerControlRelays  PropellerDeicer Timer 
LEACH RELAY COMPANY  B.F.GOODRICH 
KC-D4A  3E1150-12 
(Aft Of Firewall)  (ForwardOf Firewall) 

PowerControlRelaysandDeicerTimer Installation Figure 406
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PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

B. MaintenancePractices (continued)
11. DeicerBoots (continued)
(q) Removal of Deicer Timer (Figure 406)
Remove deicer timers on forward side of engine nacelle firewall as follows:
(1.) Remove cowl.

(2.) Disconnect electrical plug from top of timer.
(3.) Remove four screws securing timer to firewall; remove timer.
(r) Installation of Deicer Timer
(1.) Position deicer timer on firewall. Secure deicer timer with four screws previously
removed. (2.) Connect electrical plug to top of timer. (3.) Check operation of new timer to ensure proper installation and operation. (4.) Install cowls and secure with screw type fasteners.
(s) Timer Test
Before removing timer, perform the following test:
(1.) Disconnect wire harness at timer and with deicer switch on, check voltage from pin B of harness plug to ground. If no system voltage exists, fault is not with timer. If system voltage exists at pin B, check ground circuit from pin G to ground using ohmmeter. If no continuity exists, fault is in ground lead not timer. If ground connection is open, timer step switch will not change position.
(2.) Connect jumper wire from pin B of harness to B contact of timer socket and from pin G of harness to G contact of timer socket to complete power circuit. Hook-up voltmeter from ground to timer socket and ensure timer is cycling and delivering system voltage to C, D, E, and F contacts. (Starting point is not important, but sequence must be as stated.) All four contacts must deliver voltage for approximately 34 seconds each with zero voltage on three contacts not energized.
(3.) If timer meets all requirements of test, problem exists elsewhere. If timer does not meet test requirements, replace it.
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PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
CHAPTER 31
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PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL

CHAPTER31-INDICATING/RECORDING
SYSTEMS
TABLEOFCONTENTS

SUBJECT CHAPTER PAGE
31-50-00

AnnunciatorSystem 1 General
1 AnnunciatorPanel
2 Removalof Annunciator Panel
3 Installationof Annuncitator Panel
3 Removalof Annunciator Controller
3

InstallationofAnnunciatorController
4

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CONTENTS
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PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL

Indicating/RecordingSystems
A. AnnunciationSystem
1. General
The system used to provide annunciationof aircraft systems is of a two channel type: Master
Caution Warning and Advisory Alert. As a monitored system reaches a point where certain sensor
limits are reached, a circuit is made or broken thus signaling the annunciator controller to activate
a specific; red annunciator light circuit and warning horn if the system is wired into the Master
Warning Channel; or amber annunciatorlight if the system is tied into the Advisory Alert Channel.
Brightness of the lights is controlled via the Fixed Dimming Circuit. (See Schematic 31-50-01 in
PA-42-720(AdvancedTrainer)WiringDiagramManual.)
The annunciator controller is designed to illuminate an annunciator light when a specific signal is received.Depending on how specific circuits within the computer are designed, three types of inputs or signals are used to activate the controller: Ground Apply; 28 Vdc Apply; or the opening of a circuit (ground remove or positive). See Chart 1 for Index of Annunciator Controller Inputs.
　
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