The GMC CCKW

Two questions what voltage is the actual compressor and are there any technical manuals available which cover the compressor

Not sure what you mean by voltage. The compressor truck is an air compressor. Or are you asking about the voltage of the truck itself? If thats the case, then it should be 6 volts, unless converted by someone to 12 volts.

Hi
The truck is six volts but I have tried a six volt battery on the compressor and it won't turn it over. Just wondered if because of the size of the engine the actual compressor was twelve volts. I didn't want to just try it and fry the gauges/magneto

I guess I never thought about the compressor having its own battery. I always presumed that it just tied into the trucks electrical system... bad on me!!

The mag, like all mags has its own built in generator. The external lead is to short out this generator to stop the engine. If I remember right, all the gauges are mechanical. The starter is the only voltage selective item. I start mine with 12 volts