Potterton Suprima 40?

Hi I have the above boiler 7 years old and the model with the faulty PCB I have changed two - last one upgraded version. Now however we are not getting lock out we are getting a perm red light, and cannot reset it. It's like it's on standby. It will heat the water perfectly but no central heating. Been advised it may be the programmer but can find how to open this to replace. any advise greatly received. Thanks