Central Heating not working (update)

Further to my earlier post see below...
You may recall that my old (external) condensate pump appeared to have developed an electrical problem where it would cut out whenever there was a demand for it, resulting in the loss of power to the boiler and a "reboot"t. The boiler was restarted every time there was a demand for the pump.
In order to keep the boiler working in the few days until I managed to get hold of a new pump I had bypassed the pump by extending the condensate pipe from the boiler and run it to a corner under the house. Plenty of ash and soil there, and 1m+ clearance, so should have just gotten absorbed.
I followed the advice given here, and replaced the condensate pump yesterday - a like for like replacement. Took a water bottle with me, and it does seem to work as it should. I filled it up a few times.
However, one thing I noticed whilst there was that corner that the extended pipe that I had fitted to drain the condensate water to appeared dry, suggesting that the boiler does not produce any condensate water at all... The boiler had been running for a couple of hours prior to me going there.
Since yesterday I have not noticed the pump working at all. It is under the house, but can be heard if you are in the room above. I was in that room for a few hours with the boiler running, and nothing.
Any idea what is going on? The boiler seems to work fine - heating and hot water (it is a combi).
I checked under the boiler - no water there. Getting under the house is tricky, and before I go there again to check that the pipe boiler->pump is still in position (very very unlikely that it moved), is there anything else to consider (inside the boiler perhaps)?
TIA.
Have a 5 year old WB combi that is regularly serviced and works fine (I believe).
In the last two days we experienced two problems:
1. The hot water cutting off during a shower. Turning the water off, waiting for a few seconds and turning it back on resumes hot water (until the next time...).
2. Heating that cuts off at random times, and does not seem to respond to demand signal from the programmable room thermostat.
We are using one of these: https://www.wolseley.co.uk/product/center-radio-frequency-programmable-room-thermostat/ which I believe is a rebadged Honeywell basic(ish) version. I fitted it 2 years ago to replaced a failed Honeywell 927.
Earlier today I tried to create artifical demand for the heating/boiler by setting the target temp to 30c, but the relay failed to turn itself on (led stayed off). Pressing the manual/override button on the relay box turned the led on and the boiler started.
A few hours later the heating was once again not working as expected, so I repeated the above. This time the relay failed to start - the override button does not seem to do anything.
The display on the controller is bright and clear, and there is no indication that the batteries are low (there is usually a message).
- My gut feeling is that the relay box is dead. Any thoughts? - Why would the hot water keep on cutting off then? because the boiler receives random requests for heating from the faulty relay during a shower? - Any other suggestions as to the cause?
Many thanks in advance.
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JoeJoe wrote:

Can you tell if the boiler is operating within its condensing range?
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Yes I thought only sometimes did the condensing bit kick in on these boilers. Not being a boiler owner I only know about other peoples who seem to get most issues when its really cold weather. Brian
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Brian Gaff explained on 14/01/2019 :

That, due to the condensate drain freezing - rather unlikely with the present weather.
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On 14/01/2019 10:33, Andy Burns wrote:

Hold fire...
Just turned the boiler on again (it is not cold enough for the pipes to freeze BTW), and I am certain that I heard the pump working!
All's well, I hope, for now.
Thanks again for taking the time.
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It happens that JoeJoe formulated :

I run a dehumidifier in the utility, to enable clothes to be dried quickly and efficiently in there, without on making the place damp. Rather than constantly monitoring the automaticly run dehumidifier, I use a simple 'tell tale'. A clear plastic drain pipe runs down from the dehumidifier, to a drain. I have that arranged so the pipe rises so as to pass over an ordinary clothes peg, which causes the pipe to retain a small bubble of water. At a glance, I can check the bubble of water is there which confirms the dehumidifier is producing condensate and working fine, even though it might not be running at the time I decide to check it. Just a thought..
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On 14/01/2019 09:42, JoeJoe wrote:

Well it depends a bit on how much its collecting (they usually collect in into a syphon reservoir, so it can be dispensed in bursts rather than as a continuous trickle. So higher return temps will mean less collected. Many combis don't condense on DHW production.
Also you can check the condensate trap at the boiler - make sure its not blocked or full of stuff.
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Cheers,

John.
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