Have my multimeter on com (black wire) and 10A (red wire) Reading off negative terminal I get 0.55 ... how bad a draw is that ? Dial is set to AMP 10

If I remember right its suppose to be 50mA with the 24V electronics.

 

Your seeing 500mA draw which is ten times more.

What draw do you get mike ?

I need to get a special fuse for my Fluke meter to measure Amps. I blew it out years ago... (D'Oh!)

You have a 550 Mv draw. Max draw on a good system is about 30 Mv. 

Thanks - haven't worked this out yet -  pulled a few fuses and no drop.

Will let you know.