Piper Arrow IV, Maintenance Manual

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FLIGHT COMPARTMENT.
INSTRUMENT PANEL LIGHTS.
The instrument panel lights are controlled by a 5 amp circuit breaker through a switch and transistorized
dimmer control unit located to the right of center of the instrument panel. There are two control knobs, one for
the panel lights and the other for the radio lights.
REMOVAL OF DIMMER CONTROL ASSEMBLY.
1. From behind the instrument panel remove the electrical plug from the dimmer control assembly.
2. Remove the control knobs from the control units.
3. Remove the two machine screws securing the dimmer control assembly to instrument panel and
remove assembly.
INSTALLATION OF DIMMER CONTROL ASSEMBLY.
1. Position the control assembly behind the instrument panel and secure in place with two machine
screws.
2. Install the knobs and connect the electrical plug on the control unit.
ANNUNCIATOR PANEL.
DESCRIPTION AND OPERATION.
The annunciator panel is a small cluster of lights which warn of malfunctions in the various circuits or
systems. A malfunction is identified by the illumination of an individual warning light. There are three
warning lights on the PA-28RT-201 models and four warning lights on the PA-28RT-201T models. The PA-28-
201T also has a smaller light which indicates when the auxiliary fuel pump is on. Power is supplied from the
bus bar through a 5 amp fuse located behind the switch panel.
The 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 3.5 in. Hg.
The 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 below 30
psi on the PA-28RT-201 or 15 psi on PA-28RT-201T models.
The 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
through a 5 amp fuse, located near the diode heat sink, to the resistor and diode creating a no-flow condition
which does not allow the warning light to light.
The Over BST warning light used on the PA - 2 8 RT-201T is activated whenever the engine manifold
pressure exceeds 40.75 ± .15 inches of mercury. The manifold pressure sensor is incorporated in the manifold
pressure gauge.
A press-to-test button is used to check the operation of the lights when the engine is running. The lights
will work when the engine is not running with the master switch turned on. The auxiliary fuel on light is not
tested with the press-to-test button.
33-10-05
Page 33-02
Revised: December 21, 1981
2F22
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL