Baxi combi boiler short cycling on approach to central heating set point every two seconds.

[steven.roberts82]

The combi boiler when on central heating cycles about every 2 seconds when approaching desired set point. Looking at the rate of increase and decrease in water temperature between gas on and gas off there seems to be no differential. Eg if the set point is reached the boiler should not light up when it detects 0.5 degree drop. Flow in and out of the exchanger seems fine. Hot water to the taps is also fine. Is there a setting on the PCB that defines the differential temperature at which the boiler should turn off and back on again. No errors are shown . Thankyou