Hi guys really stumped with this one, hot water stopped flowing out of the shower head some weeks ago.

Hot comes from a combi boiler, cold from the mains.

Cold water is fine, loads of pressure. When thermostat set to full hot and full pressure selected no hot water at all. Hot works fine at all other sinks/bath.

What you can do is open the sink tap hot, and a little hot starts to come through the shower, the more you close the sink hot, the better the hot flow coming out of the shower. However just before you close the sink hot fully you can hear sort of a valve shutting noise from the shower and it cuts hot completely.

Things checked so far:
New thermostatic cartridge installed, no change to symptoms.
Cartridge removed and water left to flow out for 5 minutes, same with shower head
Hot water pipe leading to the back of the shower nice and hot when balanced with sink hot.

Any ideas guys? The shower is a porcelenosa system pool.

Any help would be brill. Thanks!

Hi guys, just thought I'd enclose some pics of the shower in question. There are 2 valves, the bottom one controls temp (this is where I replaced the thermostatic valve) the top valve controls which jets the water is sent to and turns the water on/off. I'm convinced the issues lies with the top valve. Do you think there are any balance valves/anti scold valves/filters that lie behind this top valve? Ive not got the tool to strip this valve yet, I'm going to bob down the tool shop soon so I can strip it.

Any help would be fantastic!

John.