Yes the problem is on zone 5... A 5 and an S do look similar now that I think about it.
Obviously that's what I was thinking given what you were saying and what I could quickly find in the owners manual. I'll admit exactly what you were saying and what I read in the owners manual didn't match exactly, it SOUNDS like to me there is a problem with the wiring on zone 5 and the controller is trying to tell you so.
If I am right, the quickest way I can think to confirm the diagnosis is to swap the wires on the controller between zone 4 and zone 5. If there is something wrong with the wire, then zone 5 program should be able to properly control "real" zone 4, and zone program 4 should show a message of "4 ERR".
This post has been edited 1 times, last edit by "HooKooDooKu" (Jun 7th 2010, 4:51pm)