I have a 3 phase 440 volt machine.
The Motor is star/Delta. When the Delta contacts, an indicater light illuminates.
The light has a trnsformer 440v AC/12V DC.
The bulb works, but why can't I get a reading of 12VoltsDC.on the lamp holder

Are you sure the "transformer" puts out DC? If it is just a transformer (no rectifier/filter), it will put out AC. The bulb won't care which it is. In most cases, if you measure AC with a meter set to DC, you won't see it.
/mike

N1ist.. Your right, Cheers! What happened is someone attempted to cut 6mm thick stainless steel in the guilotine before the Delta Phase came in, which is indicated with a lamp, which wasn't working.The machine jammed up. I got it back up & running, & the Fitter who has looked after the machine for 22years was adamant about the DC Secondary side. I'm Allright on mains Electricity, but haven't had much to do with Electronics. Do you know of any good sites, where you can get started with electronics. People have given me faulty battery chargers to fix, for power tools, I pull my hair out for a few hours, before giving up!!!

Wow!,
Great call Mike!.
Had have I noticed this post here, I would have said the same thing.
Uppeydog,
If you want to head on down to Scott35's Theory and Applications Area and post there, the guys there would be more than happy to accomodate you, not that I'm trying to send you away from here.
Also if you have any other questions please feel free to post away!.