baxi instant 105e combi boiler

[desrob]

when in hot water only mode,the temp control is in the off postion,hot water will run and the temp rises then knocks off for a few seconds and lights again the temp lights go on up until 80 degree then it knocks off,when it fires and i try and rotate the temp control for hot water the hot water light starts to flash and it knocks off straight away could it be a faulty hot water heat sensor and how do i check if the one on is faulty

 

[Puddle]

Is the hot water running when this happens,if so looks like a faulty hot water thermistor as boiler not modulating,just coming on and then over heating ,cooling and then coming on again
If it has been over heating best replace both hot water and heating thermistors as not expensive and not worth call back

 

[desrob]

Is the hot water running when this happens,if so looks like a faulty hot water thermistor as boiler not modulating,just coming on and then over heating ,cooling and then coming on again
If it has been over heating best replace both hot water and heating thermistors as not expensive and not worth call back

this model also has a safety thermostat,the heating and hot water temp sensors are easy changed would you also change safety stat aswell ,and yes i run the water it fires then i try and rotate hot water pre heat contol and it knocks off straight away