Hi,
the movement on the diverter valve on my Vailant VCW-242EH is not sufficient to allow the microswitch to be activated when the central heating system is working. On first fire-up there is no problem, but after that it is hit and miss wether the actuating lever on the diverter valve will travel far enough to close the switch. I also tried moving the screw that pushes the microswitch closer to the switch but this did not cure the problem. I removed the diverter valve and gave inside a good clean. The copper pipe control lines between the pump, servo valve and diverter valve all leaked well, when removed so I am assuming they are clear. The diaphram was intact. There is no air in the system. Can anyone give me any pointers as to what else could cause this.

David, December 2009

Also had to make an adjustment to allow a minute gap (0.2mm) between push rod and the cam on the servo. The push rod was constantly making contact with the servo not allowing it to return to the proper position via a small spring. (done by lowering the screw on top of the rod )

godfrey65, January 2010

I was also getting the problem that the movement on my diverter valve was not sufficient enough to allow the actuator to make contact with the microswitch. First thought was the diaphram. (I ordered one from my local merchant and 3 wrong ones were sent). When I got the correct one and stripped out the diverter valve only to find the original one was in good condition. I stripped down the rest of the diverter valve and found a few barnacles of crap which I removed. I reassembled everything but the problem was still there.
Following the diagnostics listed in the boiler manual, I stripped all the control lines out and they were all clear.
The manual then says to check/replace the diverter valve. I bought one from ebay for £45, which was a reasonable trade off for what I would pay to have a boiler engineer in. This had the same problem.
My next port of call was the servo valve. Not enough water pressure was getting to the right chamber in the diverter valve to allow the actuator to make contact with the microswitch. Stripped it down, gave it a good clean and all running good now

godfrey65, December 2009