Heating not functioning correctly

[Spikey123]

Hi
I have an old central heating system in my house which has been working OK up until 2 days ago.
The control unit (Potterton EP2001) developed some problems - some of the buttons stopped working and therefore I could not control on and off functions easily - so I purchased a new control box. The new control is an EP2 as this is the replacement for the EP2001.
The documentation stated that the back plate did not need to be changed so I simply replaced the control box.
I now seem to have 2 issues with the heating although these are possibly due to the same cause :-
1) The boiler is firing even though I have moved the switch to off.
2) The thermostat is being ignored and the radiators continue to be heated past the desired room temperature.
As a test I refitted the old control panel back on but these symptoms persisted. It's as if the control is now just being bypassed.

Is it possible I have damaged the heating system simply by changing the control panel or is this a simple 'user error'
I do not know much about heating systems and only have semi basic electical skills but cannot see why me simply replacing the control has resulted in this happening.
Any help is greatly appreciated.

 

[heliotrope]

Your problem is most likely due to a faulty motorised valve.

you may have one three port or two two port valves.

Check that these are switching correctly.

 

[GasmanxxxR1]

Chase the 230v round the circuit with a multimeter, programmer, stat, motorised valve, boiler. in that order.

 

[Spikey123]

Many thanks for the replies.
2 things
1) The boiler is now coming on for about 10 seconds then off for 10 seconds. It is repeatedly doing this even when the control panel is set to off. Could this still be due to a faulty valve ?
2) As stated in my original post, I have no real knowledge of heating systems and as such would not know how to check if the valve is switching. Is that something I can do or should I get a plumber to take a look ? If it's something I could do then any instructions on how to do this would be greatly appreciated