Piper Arrow IV Turbo Maintenance Manual page 472

2. Start the engine and operate at a medium RPM with the suction gauge indicating 5.0 with central air
filter. If adjustment is necessary, refer to Adjustment of Vacuum Regulator Valve.
3. With the suction gauge reading within the stated range, the gauge attached to the turn and bank should
indicate 2.0 inches of mercury. If adjustment is necessary, turning the adjustment screw, found in the valve
assembly at the back of the instrument, clockwise will decrease the suction and counterclockwise will increase
the suction. After the proper reading is acquired, shut down the engine, remove the gauge, hose and fitting
from the turn and bank and install the plug.
REMOVAL AND REPLACEMENT OF REGULATOR VALVE.
1. To remove the regulator valve, disconnect the three lines and remove the mounting nut. Remove the
valve from the airplane.
2. Replace regulator in reverse order given for removal. Check complete vacuum system for proper
operation.
INDICATING.
VACUUM GAUGE.
The suction gauge is mounted in the right side of the instrument panel. This gauge is calibrated in inches
of mercury and indicates the amount of vacuum created by the engine driven vacuum pump. The suction gauge
has a direct pressure line and a vent line. Therefore, these aircraft indicate the differential pressure or actual
pressure being applied to the gyro instruments. As the system filter becomes clogged or lines obstructed, the
gauge will show a decrease in pressure. Do not reset the regulator until the filter and lines have been checked.
REMOVAL OF VACUUM SENSOR.
Access to the sensor unit is gained by reaching up under the instrument panel to the vacuum regulator.
Removal is accomplished by the following:
1. Disconnect the two electrical leads.
2. Unscrew the sensor unit from the vacuum regulator.
3. Cover hole to prevent foreign matter from entering regulator.
INSTALLATION OF VACUUM SENSOR.
1. Screw sensor unit into vacuum regulator.
2. Reconnect the two electrical leads.
3. Perform operational check.
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
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2I1
37-20-03
Page 37-07
December 1, 1978