912UL one ignition dead

Greetings,

I'm all set to fly a new experimental, except that one ignition on the used engine I purchased is dead.   I did an ignition test a couple days ago, and it appears that I'm only running on one ignition.  From Both, when I select Left, there's no drop at all.  When I select Right, the engine quits just like I selected off.  I desperately wish this was just a wiring error on my ignition switch, but I double checked that today, and it's correct. 

I'm pretty new to 912s, but I've been reading the manual, and preparing for some troubleshooting.  First, the engine has 670 hrs on it, so the wiring isn't exactly new, but nothing appears broken that I can see.  

In the heavy maint manual, I see measurements for the ignition unit.  I have the 4 pin plugs, with the later white/yellow and blue/yellow wires, plus of course separate red for stator, and the two coil connections.  I will make these measurements this weekend, but other than a broken wire, I wouldn't expect a problem with pick up coils like this.  If one pickup was missing, would the whole ignition module shut down, or just one coil output?

It looks like this can't be a HV coil, since each one only fires two plugs, so there would have to be two out, so likely that's not the issue. 

Sadly, that brings me to my fear that an ignition module is bad.  Those things are just stupid expensive.  From the parts listing, it appears that my original part number would have been 965359, which is now replaced by 965446.  If I do have a bad module, can I just replace the one bad one, or do they both have to be replaced? 

Finally, does anyone test these modules in the US?  If I do end up suspecting one, I think I'd like to find out for sure that it's bad before spending $900+ on a new one. 

Thanks,

Rusty