it seems to be the photcell. Take off the control box and its the wee white thing at the end. Clean it and replace. If its dirty, thats your problem. They are cheap to replace. £5 or so
Gordon at fix my oil boiler. com, December 2008
why t`stat and pump? Is that circ. pump? Does your heat make it back from return to boiler?Is it a boiler? Do you need to hit reset? If not could be air bound or control [zone valve for one] problem.
