Piper Cherokee LANCE, Service Manual

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PIPER CHEROKEE SIX / LANCE SERVICE MANUAL
IX - INSTRUMENTS 03/27/08
2K10
9-6. SUCTION GAUGE.
9-7. GENERAL.
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 installed in “71 “ models 32-260-7100001 and up, and 32-300-7140001 and up, have 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.
9-8. TROUBLESHOOTING. For troubleshooting of this instrument, refer to Table IX-I of this section.
9-9. VACUUM REGULATOR VALVE.
9-10. GENERAL.
One vacuum regulator valve is incorporated in the system to control vacuum pressure to the gyro
instruments. The regulator valve is located under the instrument panel. Access to the valve for
maintenance and adjustment-is gained from below the instrument panel.
9-11. TROUBLESHOOTING. For troubleshooting of the vacuum regulator refer to Table IX-I.
9-12. ADJUSTMENTS OF VACUUM REGULATOR VALVE.
a. Loosen the locking nut or remove the protective cap from the valve, depending on which type is
installed.
NOTE: Do not attempt adjustment of this valve with the engine in operation.
b. Start the engine, after allowing time for warm-up, run the engine at medium RPM.
c. With the engine at full throttle, the suction gauge should indicate: 4.4 inches of mercury on PA-32-
260 S/N 32-1 thru 32-450 ; 4.6-5.0 inches of mercury on PA-32-260 S/N 32-451 thru 32-1110 and
PA-32-300 S/N 32-40000 thru 32-40565 ; and 5.0 +.1 -.2 inches of mercury on PA-32-260 S/N 32-
1111 and up , PA-32-300 S/N 32-40566 and up , and all 32R-300.
d. After the system pressure has been adjusted to these recommended settings; retighten the locking
nut or replace the protective cap, whichever applies to the type of valve installed.
9-13. REMOVAL AND REPLACEMENT.
a. To remove the regulator valve; disconnect the three lines, remove the mounting screws and remove
the valve.
b. Replace regulator in reverse order given for removal. Check complete vacuum system for proper
operation.
9-14. VACUUM PUMP.
9-15. GENERAL.
The vacuum pump is of the rotary vane, positive displacement type. This unit consists essentially of an
aluminum housing containing a tempered sleeve in which an offset rotor, with moving blades, is
incorporated. This assembly is driven by means of a coupling mated to the engine driven gear assembly.
The pump is mounted on the accessory section of the engine.
9-16. TROUBLESHOOTING. For troubleshooting of the pumps, refer to Table IX-I of this section.