Fagor feb20e boiler issue fluctuating hot/cold

[lucy76]

All taps fluctuating from hot to cold.(shower huge issue)
Boiler light green then amber as it kicks in for 3-4 mins with hot water, ,then going to steady red light for 10-15 seconds, water cold,
before kicking in again for hot water.
Please help
Lucy.

 

[cross thread]

Probably a scaled secondary heat exchanger, but it needs some one todo test to prove it.