Shower running cold

[Mickeydredd]

Hi
I have an oil fired AGA which is only used for cooking on, it is not linked to heating system or hot water - both of which is provided by an oil boiler.
Every year when we fire up the AGA the shower runs cold after a few minutes. Water from taps is still piping hot.

Have fitted a new thermostat in the shower but no joy.
Anyone got any thoughts on what the issue is?

 

[Mickeydredd]

The shower definately has a thermostat as my plumber changed that first

 

[Mickeydredd]

Hi All
Just a follow up to my query.

turns out it was a problem with the diverter valve in the boiler. Noticed one day that the radiators were piping hot despite the heating being off!

replaced the valve and all okay.

cheers for all thoughts and input