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Hampshire
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Woke this morning to no hot water but heating was working fine. Checked the forums and checked all the common problems:

Water and boiler pressure both ok
Timer ok (hot water set to all day)
No leaks and condenser pipe not frozen
No error codes
Tried running hot water with heating turned off

When I ran the hot water I didn’t get either the pilot light or hot water demand symbol on the boiler display. Only S code was S.7 which manual says is a heating code.

I do get the odd bursts of hot water - during this I got the S codes S.20 (warmstart demand) and S.24 (burner ignited) But the temperature was lukewarm not hot. After turning the tap off I got S.25 (fan and water pump running), and S.27 (pump overrun). Stopped running the tap, tried again 10 minutes later and back to square one - freezing cold water, no pilot light coming on and no whirring noises from the boiler.

Any idea what this could be?
 
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Combi setup with a cylinder?
 
Ok, a bit misleading with a hot water programmer (timer) on a combi :confused: try running the hot tap, press the I button and see if it recognises a demand - S.14, if it’s the newer types, press the top 2 rectangular buttons.

I’d say, it’s likely to be a diverter failure. If you try when the heating hasn’t been on, feel the flow pipe the largest pipe on the left hand side under the boiler, if this heats when running the tap, you have found your fault.
 
Last edited:
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Thanks CBE. An update - after posting this yesterday I took the front panel off the boiler and pulled down the electronic display panel to see where the diverter valve was. I just touched the diverter valve/motor to have a better look at it, then when I ran the hot water tap I got full on hot water and the tap symbol showed on the display .

I closed it all up and still today I still have hot water - no problems, so I am wondering if it was just an electrical connection problem and the act of pulling down the panel and touching the wires on the diverter valve motor has resolved it. That’s not to say I’m 100% convinced it won’t happen again, but the fact I did nothing else does make me think it’s more electrical than mechanical.
 
after posting this yesterday I took the front panel off the boiler
Let’s hope that there’s no issue with the flue then. Covers on those boilers should only be removed by competent people, who are able to perform critical checks afterwards, as it forms part of the combustion circuit.
 

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