Baxi Combi 105e wont give out hot water if heating is on!!!

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My Baxi 105e Combi boiler will not give out hot water if the heating has been on, and is still on.
When I turn on the tap or shower the LED switches across to the tap sign but the temp indicator lights reduce down to only 40 deg (i.e. only two LED's lit) and the water runs at very best luke warm!

Even if I switch the heating off it will do the same for at least the next hour or so, and only then by having the boiler set to water only does it eventually come back again.

Any ideas what it might be please because it's driving me round the bend!!!! :mad:

Many thanks :)
 
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The most obvious candidates are, in no particular order:

1. scaled up heat exchanger;
2. incoming gas pressure set too low;
3. faulty gas valve;
4. faulty supply to gas valve (e.g. PCB fault);
5. faulty DHW temperature sensor;
6. divertor valve not operating / partially stuck.

If you're not a CORGI engineer then your best bet is to find a competent one (by word of mouth recommendation) and pay him to fix it.
 
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I once had one where a kid had thrown a heavy satchel in the cupboard under the staris and partially closed the meter control valve. Boilers need full gas for hot water and doodle squat for heating.
 
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To me it sounds like a faulty diverter valve check to see if the heating pipes get hot when hot water tap is being run as it sounds like it isnt switching over and giving all the heat to the plate heat exchanger to heat the hot water properly :confused:
 
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gazthepottertonengineer said:
To me it sounds like a faulty diverter valve check to see if the heating pipes get hot when hot water tap is being run as it sounds like it isnt switching over and giving all the heat to the plate heat exchanger to heat the hot water properly :confused:

Could be, but it could be that the gas pressure is down (like Paul said), or even that the gas valve isn't operating. The last one I had like this was a Puma with a faulty PCB (although I know that a Puma without a faulty PCB is rare thing).

Anyway, my point is that it could be any of the components on the list I gave earlier, most of which require CORGI registration to replace legally.
 
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Agreed needs corgi engineer to investigate but if it was gas pressure why would it come back to normal after an hour or so as she states :confused:
 
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Thanks for all the replies everyone :D

I will give the heating pipes check a go when the hot water's running to see if that points to the problem.

I also found out this weekend that a guy I used to work with about 10 years ago is now a Corgi registered engineer and has been for about the last 6 years so he has said he'll come and take a look.

again thanks for all the replies :D
 
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gazthepottertonengineer said:
Agreed needs corgi engineer to investigate but if it was gas pressure why would it come back to normal after an hour or so as she states :confused:

I have no idea gaz! I forgot to take that into account. A sticking wax capsule is the only thing that springs to mind, but can't remember offhand whether or not the 105e uses one.
 
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