Face Mounted Instruments Removal And Replacement; Annunciator Panel; Annunciator Troubleshooting - Piper PA-44-180 SEMINOLE Maintenance Manual

INSTRUMENT AND CONTROL PANELS.
REMOVAL AND REPLACEMENT OF FACE MOUNTED INSTRUMENTS.
The instrument panel installed on aircraft S/N 44-95001 and up, consist of two all metal panels without a face
panel. When removing panels on these aircraft, ignore any references to the cover panel. Since all instruments
are mounted in a similar manner, a description of a typical removal and installation is provided as a guide.
Special care should be taken when any operation pertaining to the instruments is performed. The tagging of
connections prior to removing an instrument will help in the installation process.
1. Remove the face panel.
2. With the face panel removed, the mounting screws for the individual instruments will be exposed. Remove
the connections to the instrument prior to removing the mounting screws of the instrument to be removed.
Plug openings on gyro instruments immediately to prevent contamination.
3. Installation of the instruments will be in the reverse of removal. After the installation is completed and
before replacing the instrument face panel, check all components for security and clearance of the control
column.

ANNUNCIATOR PANEL.

The annunciator panel, located near the top center of the instrument panel, is a series of lights which warns of
malfunctions in critical systems and circuits necessary for safe operation. A malfunction is indicated by the
illumination of an individual warning light. There are three lights on the PA-44 180 (VAC, ALT, and OIL); five
on the 44-180 with carb ice detector (OIL, GYRO AIR, ALT, CARB ICE LEFT and CARB ICE RIGHT); five on
the 44-180T (OIL, GYRO AIR, ALT and two OVERBST)and five on the 44-180 (S/N 44-95001 and up) (ALT,
OIL, VAC, LO BUS, HTR OVERTEMP).
The yellow VAC warning light is controlled by a vacuum sensor switch located at the firewall and is attached
to the vacuum regulator. The sensor switch will activate when the differential pressure is below 4+ .25 in. hg.
The yellow OIL warning light is controlled by an oil pressure sensor switch incorporated in the oil line to the
oil pressure gauge and is located at the firewall. The sensor switch will activate when the oil pressure is (15 psi)
and decreasing.
The yellow ALT warning light is illuminated by current flowing from the bus bar to the alternator circuit. This
condition exists when the alternator is not operating properly and the output is zero. During normal operation,
the alternator warning circuit is also supplied with power from the top diode terminal. This current flows to two
resistors and diodes creating a no-flow condition and extinguishing the ALT light.
The CARB ICE lights are activated when a buildup of ice occurs on the light sensitive probe installed in the
throat of the carburetor. The light will remain lit until the ice has melted.
The OVERBST lights are activated whenever the respective engine's manifold pressure exceeds 36.1 to 36.5
inches of mercury.
The GYRO AIR light (44-180T) is tied into both sides of the vacuum system through vacuum switches. The
vacuum switches, which are attached to the vacuum regulators, are set to close at 4 ± .25 inches of mercury and
activate the light on the annunciator panel.
The red LO BUS light illuminates when bus voltage (14 volts) drops to battery voltage (approx. 12 volts).
The red HTR OVERTEMP light activates when the overheat limit switch energizes, indicating an
overtemperature condition in the heater vent jacket and rendering the heater inoperative.
With the battery master switch on, a press-to-test button located adjacent to the annunciator lights will check
the operation of the lights.
TROUBLESHOOTING ANNUNCIATOR.
Chart 3901 gives information on those problems most commonly experienced. For further information contact
the service representative at Vero Beach, Florida.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
2K21
3 9 - 1 2 - 0 1
Page 39-01
Revised: May 15, 1989