i have a potterton envoy 40, and for 8 yrs worked great.
now seems to have a life of its own. when its off for a while (overnight) it goes through its lighting cycle until it times out. you then switcth the power off and on again and the process goes a wee bit futher then times out again you have to stand and do this for about 10-20 mins then its fine for the rest of the day. if anyone has any ideas would be very grateful
sounds like inner casing seals require replacing not a hard job seals not expensive, also get condensate trap cleaned after 8 years will require quick clean
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.