First M715 purchase

[fliptop]

Unless the FD has monkeyed with the wiring (like that has NEVER happened before -- you'd be the first), it's not dual-voltage, just straight 24 volts. 2 @12v batteries mount in a box between teh seats.

They may have added a second battery to run things like the blinky-blinky fire lights, siren, pump starter, etc. Or just pulled 12v off of one of the two series-wired batteries.

There are two batteries wired in series between the seats, and one battery under the hood. There's two alternators mounted on the engine, a normal-looking AC-Delco and what looks like a larger one underneath (looks more like a generator than an alternator). Maybe it's not commonly called a dual-voltage system, but there are definitely two separate systems providing pixies.

They probably did add the extra battery for lights and such, but the ignition and gauges all look like they're still on the 24-V system.