Hot and Cold - Dispair!! PLEASE HELP!

Hello,

I live in a block of flats and have done since new. I've had a few problems with my pulsacoil 2000 but this was within the first year I moved in so were fixed for free.
Over the past few months, the hot water taps have run hot then cold then hot then cold for about 5 minutes before regulating and finally running hot however this has only normally lasted a day or so before being fine again.
Yesterday, the same happened but the water didn't get hot again. It ran hot and cold for about 15 minutes then ran out of hot. Today, the same. There is nothing flashing on the board that seems unusual or suggests a fault, the top tank has plenty of water in it, slightly above the recommended notch, I just don't know what to do!! I don't want to spend a small fortune (that I haven't got) if I can help it.

There were water problems in the block recently that caused a certain amount of flats from my floor and upwards to have very poor water pressure but they fixed that.

I'm just really fed up with having a shower that takes double the time because I have to leep stepping back when it goes cold!!!

Anyone who could give me a clue as to what it might be I would be very grateful.

Nicki

Could be temp sensor or PHE sensor
The pump or pump pcb
Have you a good flow rate out of the hot taps whether hot or cold?
If it is slow could be blocked Y strainer filter / reducer
Or PHE is scaled up. How old is unit and is the water hard in your are?
Mike

Also check the water level in your header tank is correct.