Baxi 105e Instant no hot water shower

[mruseless]

Help, I have a Baxi instant 105e boiler. For the last two months i have been trying to solve the problem of not getting hot water to the shower. The CH fires up and runs well. The hot water to the taps run fine, upstairs and downstairs. At first i thought it was the shower, so I replaced the shower cartridge (Mira Thermostatic) at a considerable expense. The boiler fires up and runs well. The LEDs indicates no fault, and still I am receiving luke warm water to the shower. Initially the shower is hot when turned on but the temperature decreases after a few minutes. I have replaced the diaphragm in the boiler but the problem still remains. Any help will be greatly appreciated as the wife is driving me nuts moaning.
cheers

 

[picasso]

take the head off the shower and see if the temperature stabalizes, if it does then the head is restricting the flow making the boiler modulate down.

 

[45yearsagasman]

To prove that the boiler is ok,Check the hw outlet pipe directly under the boiler with the shower running.If the outlet pipe is constantly hot then you have proved that the boiler is ok and delivering constant hot water and that the fault is elsewhere.Are you sure that in hw mode the rad circuit is not heating as well? indicating a faulty diverter valve.

 

[mruseless]

Hi thanks for your response, Ive just ran the hot water and the domestic HW outlet pipe and the heating flow pipe (rads) under the boiler are baking hot. I presume this means the diverter valve needs replacing? Do you have an idea of how much this cost?

 

[mruseless]

Can anyone help again please. While running the hot water tap upstairs the outlet water pipe from the boiler is piping hot, the same as the boiler HW outlet pipe. I also felt the heating flow outlet pipe as well from the boiler and this was piping hot although the CH was not on. The radiators are stone cold apart from one which a 1/4 luke warm. Now running the shower, this initially becomes hot but then becomes luke warm. On feeling the HW outlet pipe this is also luke warm but the heating flow pipe is piping hot. Can anyone confirm that this means the diverter valve is definitely faulty? Any more checks I can do?

 

[45yearsagasman]

Those are classic signs of a faulty diverter valve.No heat should pass to rads when HW is on.I always repaired these with a service kit,but others prefer to change the complete valve.I no longer have access to part numbers,but there are some helpful people on here who will supply info.This is diyable albeit a bit involved.