Cessna Master/Split switch wiring

[mike109g6]

Purchased a cessna style master/split switch from A/C Spruce in order to eliminate toggle type switches for isolating the battery in the event of an alternator failure. Problem is that it did not come with any wiring diagram or have any of the tabs on the back of the swich marked. AeroElectic schematic Z-11 shows using it but it is not the same style switch that I received from A/C Spruce. Has anyone out there used this type switch and if so do you have the wiring diagram denoting which tabs go to what? I realize that 3 tabs are for the alternator side and 3 for the battery side but 2 are doubled tabs on each one but not layed out the same, ie battery side has double top single bottom and alternator side has single top and double tab bottom. thanks in advance. Mike H 9A

[asav8tor]

Both on=Bat & Alt on

Both off=Bat & Alt off

Split=Bat on Alt off

Turning Alt on forces Bat on

Turning Bat off forces Alt off

Take your ohm meter and figure out off/on checking the fast on tabs until you get the above results.

The idea behind this switch is to prevent the Alt on with the Bat off which could result in "smoke in the cockpit".

Very bad thing: Alt running with the battery disconnected.

[w1curtis]

You do realize that the primary purpose of the Cessna style split master is to prevent running the alternator without the battery and since most early Cessna's did not have pull-able breakers, it allowed you to easily take the alternator "off-line" by eliminating the power to the field winding.

As far as "isolating the battery in the event of an alternator failure" all it does is break the field wire. You can do the same thing by inserting a pull-able alternator field breaker.