Alternator ON or OFF

[Trent 972]

For a Cessna the manual more than likely says to leave the alterntor off until it starts.

From a Cessna 182 POH

MASTER SWITCH
The master switch is a split-rocker type switch labeled MASTER, and is ON in the up position and off in the down position. The right half of the switch, labelled BAT, controls all electrical power to the airplane. The left half labeled ALT controls the alternator. Normally, both sides of the master switch should be used simultaneously; however, the BAT side of the switch could be turned ON separately to check the equipment while on the ground. To check or use avionics equipment or radios while on the ground, the avionics power switch must be turned ON. The ALT side of the switch, when placed in the off position, removes the alternator from the electrical system. With this switch in the off position the entire electrical load is placed on the battery. Continued operationwith the alternator switch in off position will reduce battery power low enough to open the battery contactor, remove power from the alternator field, and prevent alternator restart.

Some people may have educated themselves to a greater level of understanding then mere compliance with the POH, but by the offering of and acceptance of that advice you are replacing the ‘Lowest Common Denominator’ with an unknown denominator for people who have yet to gain their own extended wisdom.