[AT] OT Buck-Boost convertor for charging auxiliary battery

[James Peck]

https://goo.gl/images/zLNCXu

Offiler <snip> According to this schematic, the regulator is powered and sensing off a separate diode trio (separate from the main rectifier) via the D+ line.  The D+ connection typically goes to a dash warning light.  The regulator has no connection to either B+ or W.  You know what B+ is.  W is an AC signal output, which one random web references calls "Waveform" possibly used for diagnostics or a tachometer.

] Cecil Bearden] I need some help with the wiring on my MTZ 1220.  in an earlier post I mentioned that this voltage convertor (VC) will not keep the auxiliary battery charged.  The factory furnished a new VC and the dash warning light indicates that it cannot keep up with the battery when using the lights, or the cab fan.  Perhaps the alternator is not providing enough current on the main battery, or the signal from the alternator is not triggering the VC to operate.  
I have tried to convince the factory to change over to a 24V alternator and use one battery for the 12V accessories.   The alternator is an ISKRA brand  and a one wire Delco is not easily mounted the way the ISKRA is..  The only wiring diagram of the alternator shows a battery connection and the sensor connection to the alternator.  The W terminal is not shown to be connected in the diagrams I have.   I need to know if the ISKRA alternator uses the battery terminal to sense the voltage for the regulator as a one wire Delco does, or if it need a wire to the W terminal to turn the alternator on.   If it uses the Bat terminal then changing to 24V won't be a big deal.  If the W terminal or another needs the 24V input, then I will have to install a relay to turn on from the ignition switch as the ignition switch is on 12V.   the starter and the glow plugs are 24V.  To change over to the 12V system as the factory has suggested, will require changing 6 glow plugs, the starter, alternator, and new cables.  My solution only requires changing the alternator.
I know some of you guys are much better at reading electric diagrams than I am.   I can usually wire things up without any trouble, but sometimes wiring diagrams give me trouble.  If you could take a look at the attached, I would certainly appreciate it..