I have a 16 zone IRO and I am only using 9 of the zones. 8 on the left side and 1 on the right side. I only have 1 common wire. I put it on the left side and everything works fine for the first 8 zones. The 9th zone won’t fire up and of course I assume it’s because the right side doesn’t have a common wire. I tried to cheat and ran a write from the left common to the right and that didn’t work.
Any suggestions or do I need that second common?
It should work fine - I have only one common and 12 of 16 zones running fine. I would trace the common back to make sure that the solenoid in question is continuous to the common on the Iro.
I have the same exact scenario and it fires with no problem. 
Try switching the zone with another zone and see if if happens you may have a bad solenoid. Just guessing. 
Is the one common hooked up to the left or the right side of the Iro. Mine is on the left but I am not sure if that makes a difference.
Is the one common hooked up to the left or the right side of the Iro. Mine is on the left but I am not sure if that makes a difference.
Hi there I also have the common connected to the left side of the IRO. 
If you have tried what I suggested before and that didn’t work Try placing the wire on no 10 position and see if you can get it to fire there.
It should work with just one common on all 16 stations regardless of location. 
@Garden_Dude, just checking in to see if you got Zone 9 to fire yet? The common terminals are shared between the left and right terminal blocks. There’s no need to install a jumper between the two white terminals.
Great idea @JNotar! @Garden_Dude, did you try testing like this yet? If we can get Zone 9 to fire on another terminal, then we might have a defect in your wallmount. If Zone 9 doesn’t fire on any terminals, then we need to troubleshoot the wire and/or solenoid.
Please keep us posted.
Best, Emil