switchmaster 805 problem

[penderri]

Ok, i have a elderly Baxi gravity feed boiler that services my hot water and heating.
I have it cleaned and checked on a regular basis, however some time ago the constant water selection button on the 805 switchmaster just stopped working leaving me the only option of pressing the heating and water constant/timed selection.
When i queried this i was told the 805 had died and needed replacing. I purchased a new 805 and as it is virtually "plug and Play" i replaced it only to find that the problem is still there!
I now have 2 805 switches and a very hot house! Any ideas?
regards,
Penderri

 

[twgas]

can you have hot water on by itself when it's timed?
do you have a 3-port valve, 2* 2-ports, or Gravity hot water

 

[penderri]

Hi, no hot water unless switch in constant heating and water, also not sure about ports/valves but i know it's gravity feed system. If this helps?