10-42a. REPLACING ENGINE GAUGES AND SENDERS
Original equipment A.C. Sparkplug and Stewart Warner engine gauges and senders are no longer
available. Rochester gauges and senders have been identified for service replacement. See the Seneca II
Parts Catalog, P/N 761-589, or Service Spares Letter No. 406.
10-43. MANIFOLD PRESSURE GAUGE SYSTEM.
10-44. GENERAL.
The dual manifold pressure gauge is a vapor proof, absolute pressure type instrument calibrated from 10
to 50 inches of mercury. Incorporated in the gauge are switches that complete the annunciator panel
circuit whenever engine manifold pressure exceeds 39.5 inches of mercury. The manifold pressure lines
have drain valves located behind and below the fuel manifold pressure gauge. This allows any moisture
which may have collected from condensation to be pulled into the engines. This is accomplished by
depressing the two valves for 5 seconds while operating the engines at 1000 RPM.
NO
TE: Do not depress the valves when manifold pressure exceeds 2.5 inches Hg.
10-45. TROUBLESHOOTING.
PIPER SENECA II SERVICE MANUAL
X - INSTRUMENTS 01/01/09
2F4
TABLE X-VII. MAGNETIC COMPASS (cont.)
Trouble Cause Remedy
Card sluggish (cont.) Excessive pivot friction Replace or repair
or broken jewel. instrument
Liquid leakage. Loose bezel screws. Replace or repair
instrument.
Broken cover glass. Replace or repair
instrument.
Defective sealing Replace or repair
gaskets instrument.
Discolored markings. Age. Replace or repair
instrument.
Defective light. Burned out lamp or Check lamp or continuity-
broken circuit. of wiring.
Card sticks. Altitude compensating Replace or repair
diaphragm collapsed. instrument.
Card does not move The gears that turn Replace or repair
when compensating compensating magnets instrument.
screws are turned. may be stripped.
Compass swings Normal.
erratically when radio
transmitter is keyed.
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