Hot then cold water from shower

[Tazie]

I have a performa 28... Generally it is working fine. But when having a shower the water is going from hot to cold then hot then cold???? Why is this???!

 

[zanwan]

Is the shower electric or thermostatic?

 

[BlueMoonMole]

Potterton Performa 28 - System or Combi?

Its either the Shower or the Boiler, we just need to determine a few things to work out which

 

[Agile]

Does the water at the taps do the same thing?

Tony

 

[Tazie]

The shower is attached to the bath,,,, I think it does do it to the taps as well.
When using h/washer it does and washing up

 

[Whitespirit66]

When the water runs cold, do any of the indicator lights on the boiler control panel come on?

 

[Tazie]

No, What I have noticed is that the pilot light goes off then comes on

 

[Tazie]

Update: it's a combo boiler, the shower is nor elec nor power shower its an attachment to a mixer bath taps,,, I think it only goes cold when the temp light hit 80 degree on the front panel of the boiler,, which it reaches very very quickly appo in seconds .... Any ideas. The heating works fine. But all the taps in kitchen and in bathroom are same. Hot then cold hot then cold