Shower conundrum

[Golaboots888]

Hello

I posted a while back about my Bristan Prism shower not supplying the correct temperature of water.

The filters are clear, there is plenty of hot water.

I suspected the pump, but turning it around yields the same performance so it can't be the pump.

It seems to work with a slow flow (pump off) but not a faster one.

I'm left with two possibilities I suppose:

1, air lock somewhere in the pump.
2, faulty thermostat unit.

Neither seems especially likely to me. I would have thought that draining the pump and running with the pump off would clear any airlock there. The fact that everything is ok when the pump is off makes me think that the thermostat is ok.

Any ideas?

 

[Goldspoon]

I am not sure about this but I had a shower and the water temp gradually declined.

I changed the cartridge (after asking for advice on here).

This worked.

 

[Golaboots888]

I am not sure about this but I had a shower and the water temp gradually declined.

I changed the cartridge (after asking for advice on here).

This worked.

Did it get hot again and cycle downward if you stopped and then started the shower again?