I've had an engineer out to my house a few times about this problem but still no joy so hopefully you can give me some information.
The heating comes on every day on the timer but only for the hot water, the only way we can get heat into the radiators is to manually fick a switch on the red box at the boiler and it comes on. At the minute he has overrided the thermostat and it just comes on at full heat (which so unbearable at times). He says that next if its not the thermostat (which it's not) he will have to drain the whole system and is unable to give us a price for the job. Can you help with this please.

CJ, March 2009

It sounds like a motorised valve has stopped working.These have a synchron motor inside which pop and can on most valves be changed without draining the system.If the valve has gone completely then a drain down may be needed and a complete new valve fitted.Thats when things get expensive.A synchron motor can be bought for less than a tenner.

Tony S, March 2009