Power Shower - Hot/Cold problem.

[boultona]

New to this form, so please excuse my knowledge, but I need help with a show problem.

We have a power shower (10 years old) in the en-suite. Its a Triton mixer (don't know model) the pump was replaced around 4 years ago after a leak and its a dura speed pump.

The mixer tap looks like this except we dont have the white surround, we have the chrome affect bar.

The water feed is :-

• Cold - fed from tank in loft
• Hot - fed off the top of the hot water tank in the airing cupboard. This is also where the pump is

The problem we have is with temperature.
Most days we get no hot water through to the shower regardless of the setting on the mixer. If we turn the cold feed tap off into the pump, the hot only has a varying pressure, if i turn the mixer up to 6-7(out of 10) its got good pressure and very hot, but if I turn it back sometimes it stops at 4 sometimes it stops at 2. At this point the water is too hot to use. We then add the cold feed back in to the pump. we have to be careful, to high and it stops the hot. too low there is no pressure. With the shower at 4 (out of 10) the shower is almost too hot to be in it.

What is the problem? Can I fix it?

Any help, advice will be appreciated.

Thanks

Tony.