my potterton EP4001 timeswitch has a large A in the bottom left corner of the display and now the controls no longer work. The boiler is now set to continuous and the clock won't change nor can change the setting from continuous to Auto. How do i get this to happen

Graham Mace, December 2009

Take the top panel (timer box) off and on the back of the removable timer box there is a security switch which can be turned to "on" or "off". in the ON position this locks out the user controls and in the OFF positiion this allows use of the digital settings.

Macc Mark, January 2010