A: To check wither you have a boiler or shower fault
Turn the shower on as usual, try and get a hold of the pipe going to the shower, if you can’t get to the pipe at the shower you may be able to get to it as it leaves the boiler.
What ever the temperature is on/in this pipe, the shower can never get any hotter than that (So if the temperature is cool then something then at the boiler is not allowing the water to heat up enough)
The other fault is wide variations in the temperature of the water leaving the boiler.
If all the above are OK then I would give the valve a strip down clean lube and fit a service kit
http://www.showerdoc.com/TRITO-83304890-Triton-Service-Kit---Pc-2100-83304890
Answered 200 days ago | The Doc