Baxi 105e hot water fluctuating

[jjb1333]

Hi
I have a Baxi 105e I have just had a new PCB fitted following a fault .
Boiler now works fine except for a minor problem which wasnt there before the repair
When using the shower the water is nice and hot and then after a couple of minutes the water temperature drops to just warm them picks up again to nice and hot again
It does this fluctuation in temperature about every minute.
Could i have some advice please ?
Thanks.

 

[durhamplumber]

Could be your shower.What is water like out of tap?Common fault is thermistor too.

 

[gas112]

just on shower ? not on taps
then it is the venturi in boiler that has fell apart very common fault and totally unrelated to board change , just coincidence

 

[jjb1333]

yes it seems to be ok out of the taps so i guess it must be the shower mixer tap, I didnt think to try the taps before
perhaps it was just coincidence since i had the pcb fitted to the boiler
Thanks very much....

 

[gas112]

it wont be the shower mixer

 

[jjb1333]

Is the venturi something i could check myself ?

 

[Hot&Cold]

Is the venturi something i could check myself ?

yes you can do a visual venturi check but hopefully the shower mixer is suitable and correctly set up for combination boiler use,otherwise your wasting time.

the venturi cartridge includes a fliter and a flow regulator,its a common fault area but easily temporarly removed to check/clean. needs a 24mm spanner or similar

the venturi is in the white part on the end with a spring,it should be intact when removing the cartridge carrier.

 

[jjb1333]

Yes
I have had the shower mixer installed for about 5 years and never had a problem before
Where is the Venturi situated ?

 

[durhamplumber]

it wont be the shower mixer

Why

 

[mcmoby69]

Blocked plate.

 

[gas112]

Why

because unlike you i know what i am talking about

 

[gas112]

Blocked plate.

really ? why is it working ok out of taps then ?

 

[mcmoby69]

really ? why is it working ok out of taps then ?

Should have said partial blockage tbh. Amount of water going through plate is reduced , water gets up to temp quicker so thermistor acts correctly.
It's also possible the shower head needs cleaning or a non return valve is stuck open.
Usually the hot side on the shower.

 

[gas112]

shower gets up to temp thermostat within it cuts down hot flow , due to ventuuri in boiler being in bits the pressure behind diaphragm is not correct and pin comes back off micro switch shower goes cold stat within opens up increasing hot flow pin moves back out onto microswitch

 

[nwgs]

It’s always worth checking Venturi with a HW issue relating to shower. I’ve cured it a few times now with a new Venturi.

I wouldn’t even know about it if it wasn’t for the CC and gas112.