Baxi 105e combi not heating tap water

[cliff1959]

Hi,
First post newby here.
Don't know if anyone can suggest why my boiler has just stopped heating hot water to my taps.
The CH works ok and no lights flash telling me there's a fault.
If I turn the main knob to hot water only it then heats the water but of course the CH stops.
Could it be the PCB as a friend suggested?
Any ideas welcome.

 

[Billy Bob Bob]

if its seeing a demand for dhw but not firing it could be a diaprahm,a divertor or a plate heat exchanger dumping down you need to call in a reputable gas engineer its highly unlikly to be the pcb

 

[cliff1959]

Thanks Gasman. Another clue for you is the pressure reading drops to 0.5bar when the heating's off, but jumps to 2.5bar when it's running. Is this normal?

 

[Billy Bob Bob]

Thanks Gasman. Another clue for you is the pressure reading drops to 0.5bar when the heating's off, but jumps to 2.5bar when it's running. Is this normal?

no and unrelated to your first fault,unless your plate heats burst but more than likely your expansion vessels shot

 

[cdgas]

Check the pressure relief pipe outside, if you have staining on the wall running from the pipe then your expansion vessle is goosed, you will hve to get this replaced as well as the pressure relief valve. You can if you have space fit an external expansion vessel this saves a lot of hassel with getting the old one out from behind the boiler. Your hot water problem could be the PCB as you are getting C/H but no hot waterwhen changing to Hot water only you get nothing. Could be an expensive repair with both sets of problems, get some quotes for repairs and replacement of boiler. The potterton Promax 28 HE fits straight back onto the existing wall mounting jig as long as you use a 45' flue bend to get back out the old flue hole.

 

[RoryD]

You should have 1 - 1.5 bar when cold, this will go up when hot. Gasman was right, get a gsr bloke to check the diverter out, there is a service kit available