Ferroli Modena 80E running hot then cold then hot

[siwilks]

Hi,

I've just moved house and the boiler we have tends to (particularly when showering, frustratingly) do alternating spells of hot and cold of at most 30 secs. Also, when you turn the temp up or down on the mixer it takes a long time for the change to happen and there is a fine balance on the mixer between scalding hot and freezing cold.

Any help would be amazingly much appreciated!

Thank you,
Si

 

[JonB]

Probably wants both thermisters changing, £10 for bits at the most.
JonB

 

[bribhoy]

Fan venturis have a habit of "disintegrating" - i've found a few outside having been spat out the flue by the fan blades, this can give HW hot/cold/hot