combi oil Worcester greenstar heatslave 12/18 switches off?

I have a internal combi oil Worcester greenstar heatslave 12/18

Its has a built programmer and Hot water temperature control and Central heating temperature control dial both marked from 1 to 6.

The minimum and maximum ranges of the heating control positions are approximately 55°C to 80°C.



Pressure bar is 1.0 and its a sealed system.

Increased and decreased thermostatic radiator valve settings on rads.


The combi is connected to 6 radiators with a 15mm pipe work, all the rads have been bled.

There is no separate controller for the timer or thermostat as they work from the front of the boiler).

The lock out light is off, and there is plenty of oil.

The Problem:
The boiler only functions for a a few minutes at a time on the central heating side.

Hot Water:

When you switch on the boiler for the hot water you can hear the boiler igniting and working,
But the hot water only comes on at the high setting of the heating temperature control dial marked 4 out of 6, it used to come on at setting 2, the water is nice and hot. But the setting is far too high.

Central Heating:

When you switch on the central heating dial controller, nothing happens until you set the dial to 5 out of 6.
The boiler again ignites and sounds like its working, but after 3-4 minutes the boiler makes a clicking like sound like the thermostat has reached its set temperature and then switches itself off.

The boiler used to operate from the setting dial marked 2 out of 6 and now on setting 6 the highest level the central heating doesn’t come on for very long. As it seems to have reached its setting.

And the boiler is very hot.

When I called the manufacturer they told me that there is no built in thermostat on this boiler.
Not really sure what they mean by this.

There is only one reset button for the ignition but none for any other thermostat or controller.
I have turned the boiler off and left it over night and it still goes back to the same problem, its getting too hot and it seems like the temp has been set too high, regardless off the setting of the temp controllers.

Also one last thing, the Optional programmer built into the boiler had a test feature- will this help me remendy this problem using a wi fi version or will the temp heating controls on the front of the boiler over ride this.