Worcester Central Heating Constantly Switches On and Off

[stricklandsp]

Hi, I hope that some kind soul out there might help me with a Problem with a Worcester 24cdi combi boiler. The system is controlled by a "Lifestyle 711" timeswitch (standard two timer on /offs per day program))and I have a single thermastat in the hall.
Problem is that when the thermostat is turned down so that it is "off" the Central heating part of the boiler keeps firing up for a few seconds and then switches off after a few seconds and then on and then off..... etc.
If the electronic timer is "off" then no problem or if the themostat is "on" it works fine and heats the water like normal. No problem with the hot water in the taps.
I thought it might be the timer unit so fitted a new one..... no change and still had same problem.
Havnt looked at the wall thermostat and have to say its pretty old but can hear click on and off as you rotate it. Also when the problem is happening it doesnt click on and off constantly so dont think it is that... that said could be wrong!!!
Any ideas would be really appreciated . Thanks in advance!!!

 

[ChrisR]

Is the boiler getting hot?
Turn power off and wait for it to cool right down, then when you turn on see ifit stays on longer (getting hot) that if it's been on a while.

COuld be water flow switch faulty /sticking.

Does the CH work ok if you turn it up?

 

[stricklandsp]

HI Chris .firstly thank for taking the time to reply.... appreciated
The CH works fine if the timer and room thermostat are on.... so that is good I guess if I dont get it sorted by "winter"
The problem is when the timer is on either on timer setting or simply "on" and the room thermostat is tuned down to really low or effectively off. For some bizare reason the boiler keeps on firing up for a few seconds and then offf.. then on then off etc. It is heating up the radiators (obviously not hot as its only on / off all the time)
Will turn it all off tonight. so it cools right down and then see in the morning what it does when I turn it on.
Thanks

 

[stricklandsp]

Well I left the whole system turned off all night at the mains switch so it was stone cold. Turned it back on and first 7 or 8 clicks it was the same... ie on for a second and then off for a second. On 8 or ninth time the burner CH light and ignition light came on abd could hear burner ignite... it stayed on for probably a couple of minutes before going off. Then went back to on off every few seconds. Dont know if this helps but exact sequence of the lights coming on and off is. CH light on ... second later ignition... second later ignition light off.... CH light off.
Does that help or give any clues??
Cheers