Re the C vs Ku thing, your switch never sees either C or Ku. The signals coming from the lnbs are IF in the 950-1450 range, not C or Ku. Ie no difference at all.
Several years ago I bought a 4 port switch to upgrade my 2 port. It was dead out of the box on 1 port, and over a period of a few months, lost the other two ports, so several months ago, I bought 3 new diseqC switches of different brands. All were completely or partially non-functional, so I put them all back in their boxes. Then last fall, I had a new need for a switch, so I pulled one of the bad ones out, and for some reason it worked, and has continued to work for the best part of a year now. I've also found that one of my switches wouldn't work with one receiver, but then worked well after I upgraded the power supply (computer receiver). I've also come to the partial conclusion that switches don't work as well when close to the receiver compared to close to the LNB.
I've come to the opinion that using DiseqC switches can be a black art. Sometimes they work, sometimes they don't. I'd recommend buying a couple spares. If one doesn't work, exchange it for another, but don't throw bad ones away, because they may start working again, or may work with a different receiver.
Also, make sure you have LNB power turned on in the receiver. The switches need power.
Seems like in the
mercury, there are 2 items you have to set up, ie you have to set the
diseqC switch type (1.0) and select the port in another item, while other receivers it just goes from off to the proper port number in one item (hope that makes sense).
When you changed the ports are you sure you have both the correct port number and LO programmed in receiver?