Cessna 172N Engine Instruments

Cessna 172N Engine Instruments
Fuel GaugesOil Temp and PressureSuction GaugeMaster SwitchPrimerMagneto SwitchAmmeter

Fuel Gauges

The fuel gauges show the quantity of fuel in each tank; however, the fuel levels should always be checked visually and/or the fuel levels verified with a calibrated fuel stick.

Oil Temp and Pressure

The Oil Temperature and Oil Temperature instruments show their normal ranges as a green arc.

Suction Gauge

The suction gauge indicates whether the vacuum pump is providing adequate suction to the gyroscopic flight instruments; it should be in the green range during runup and in flight, but it is normal for this instrument to indicate below the green arc at idle.

Master Switch

The Master Switch controls power from the airplane's battery and alternator. Operating with the Alternator side of the switch off will eventually lead to a depleted battery.


The engine primer is sued for engine starting; it should be confirmed to be in the in and locked position prior to takeoff; a primer which is not secured can cause a rough running engine.

Magneto Switch

The magneto switch allows the pilot to check each of the engine's two magnetos independently. It should be verified that the switch is in the BOTH position prior to takeoff.


When the engine is running and the master switch is turned on, the Ammeter indicates the charging rate of the battery. If the electrical load exceeds the alternator's capacity, or if the alternator is inoperative, the ammeter indicates the discharge rate of the battery.