One side dies on runup

I would start by swapping the connectors between ignition modules A and B. If the fault moves to the other ignition then you have a problem with the module, if it stays on the same ignition then you have a wiring/switch/charging coil problem.

Ignition switches can be a problem but they tend to fail open circuit, not short circuit. The charging coil connections on the early engines were problematic where the red wire connects to the ignition module. Let us know what you find.

Suggest viewing latest Lockwood video on Rotax-owner.com

Troubleshooting the Rotax 912/914 ignition system

That video is good if you have modules with 2 x 6 pin plugs.

If you have an older ULS with modules with 1 x 6 + 1 x 4 + 1 x1 pin plugs be careful, it can mislead you! You have to work it out carefully from the wiring diagram.

Pete I recall an AD on ELA gyrocopter switch modules. If you find it is the switch I will chime in again.

Regards......Chook.

So here’s some additional info;  I started the engine and got to normal operating temp.  Set the idle at 2300 rpm, then turned off ignition b with no resultant drop in rpm.  Cut ignition a and the engine quit.  Repeated several times, same result.  Then engine spontaneously went from 2300 to 2500 (on its own).  Turned b off, rpm dropped, turned a off, rpm dropped (normal behavior).  So it seems like b is not activating like it should, taking its time to come on line.  Does this sound like the module to you guys?