The spindle is free so I suspect it's te programmer or thermostat. I can't figure-out how to open the programmer though. I presume the front should come off. Is there a catch, or do I force it off?
Check the seals. Ours leaked from where there was a split in the seal around the door. I fixed it temporarily with silicone sealant, before replacing the complete seal. The temporary fix lasted for ten weeks!
Today we discovered that we have no hot water to the radiators but lots of f(airly?) hot water to the tank and taps. The boiler ( an Ideal E Type CF - as old as its Jaguar namesake!) is working. I'm not sure about everything else. The system also includes a Grundfos Selectric UPS 15-50 pump, a...