Piper SEMINOLE PA-44-180, Maintenance Manual

Page: 368 / 881

ELECTRICAL TESTS.
1. With engines “OFF” turn ON - Master Switch.
2. TIMER: Activate the De-Ice System Switch. (Caution: Do not hold Surface De-ice Switch in “ON”
position. This switch is a momentary spring loaded center-off switch.)
A.
Check Timer operates immediately.
B. If Timer does not indicate operation, check aircraft power from Circuit Breaker through switch, to
Timer. Also, check for proper ground.
C. If no electrical faults are present - replace Timer.
3. LEFT & RIGHT CONTROL VALVE SOLENOIDS: Activate the De-Ice System Switch and run engine.
A. Check both Control Valve Solenoids actuate. (An audible “CLICK” can be heard or the action can be
felt by holding a hand against the unit.)
B. Check system pressure begins to build in the boot system.
C. If pressure does not build (check LIGHT on control panel after 6 seconds) Control Valves are suspect.
D. Disconnect electrical leads from Control Valve Solenoids and measure power is available when system
is activated. Also confirm ground is good on BOTH SOLENOIDS.
E. If problem is not electrical - perform “TEST FOR PRESSURE LEAKS”.
4. DEFLATE VALVE ASSEMBLY: Activate De-Ice System Switch.
A. Check LIGHT glows on control panel after system pressure builds to 10 P.S.I. Continue to monitor
system as pressure continues to build to 17 P.S.I. system pressure, or 6 seconds, whichever occurs
first.
B. Control Valves should actuate and dump pressure overboard.
C. As pressure decreases below 10 P.S.I., LIGHT should extinguish as cycle is completed.
5. If Step 3 shows Control Valves to be operating correctly, but Step 4 shows system cycle to be faulty, and
system “Test For Pressure Leaks” shows no leaks; check DEFLATE VALVE ASSEMBLY.
6. DEFLATE VALVE ASSEMBLY:
A. Check power applied to Deflate Valve and confirm grounds are both good. If no electrical faults exist,
replace Deflate Valve Assembly
TESTING FOR PRESSURE LEAKS.
1. This test can be performed in either the left or right nacelles.
2. Cap the overboard ports of the control valve.
3. Connect a source of clean air to the inlet port of the control valve. It is necessary that the inlet pressure be a
minimum of 18-20 psig pressure to the system. By means of a hand operated valve, trap the pressure in the
deicer system. Observe the system for leakage. The leakage rate should not exceed a pressure drop of 3.0
psig per minute.
4. Remove test equipment, lubricate all threads, and replace all system components.
COMPONENT MAINTENANCE AND REPLACEMENT.
FILTERS.
Air supply for the system is supplied through the vacuum system. Refer to Chapter 37 for replacement of the
appropriate filter(s).
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
3 0 - 1 3 - 0 1
Page 30-08
Revised: May 15, 1989
2D12
PIPER AIRCRAFT