Perko Battery Switch

[nial]

I have one of these in my boat, four position rotary switch, installed in 1987.
How can I tell if it has an automatic field disconnect feature built in? When I look at the wiring I see the usual heavy wiring from the batteries and to ground but also two light wires going to I don't know where. All comments appreciated.
nial

[Maine Sail]

Originally Posted by nial

I have one of these in my boat, four position rotary switch, installed in 1987.
How can I tell if it has an automatic field disconnect feature built in? When I look at the wiring I see the usual heavy wiring from the batteries and to ground but also two light wires going to I don't know where. All comments appreciated.
nial

There will be a small brass nut and stud on the back, much smaller than the other three. If I recall it takes a #10 ring. It should be marked "AFD" or "Field Disconnect" or something to that effect. This terminal breaks/disconnects slightly before the OFF position does so the field to the regulator is cut before the battery/load is disconnected.

You can also get around frying the diodes by wiring the alternator direct to the house bank so it always sees a load. It is wise to fuse this wire close to the battery though if doing this.

[GordMay]

Yes, the two smaller terminals (F1 & F2) are the AFD switch, wired to the Alternator or Regulator.
➥ http://www.perko.com/images/catalog/...603INS1%29.pdf