What is wrong with my Potterton Puma 80?

My porterton puma 80e is constantly calling 4 heat even though the switch is on off which i believe is right in the middle.

al
March 2007

Expansion vessel is flat. Open pressure relief valve and find the point at which it stays stuck open. at the back of the boiler, you will find a big disc shaped part behind the boiler on the wall, usually red, with a car tyre style pump up point. leave the pressure relief valve open, attatch a foot pump and pump it to 1 bar. if this is working, you should get some water out of the pressure relief pipe. remove the foot pump and close the pressure relief valve. refil the boiler. problem should be solved. if not, new vessel required.

craig, plymouth
May 2006