Baxi Combi Instant 105e - no hot water

[ftual]

Hi

My 8 years old Baxi boiler had been giving only warm water for the last few months. I thought the issue was the secondary heat exchanged so I had it replaced. Unfortunately, this made things worse: the water is now only lukewarm. The symptoms are the following ones: when hot water is requested the boiler fires up but shuts down after only about 10 seconds and will only come up again 10s of seconds later. It will then have the flame on for about 10s and shut down again etc..
N.B.: the control PCB is new.

Any idea?

Thanks for any suggestion.

 

[BlueMoonMole]

Before looking at the Secondary Heat Exchanger and PCB...

Did you not think to check if the DHW Microswitch was fully making, and consider checking/replacing the DHW Diaphragm?

It's an intermittent fault, and could be a number of things, but that's a much cheaper & easier thing to check.

 

[ftual]

Hi BlueMoonMole

Thanks for your post.

PCB was not changed for this issue but for a previous one.

Microswitch does work: the behaviour of the boiler is exactly the same if I trigger it myself with a screwdriver. Diaphram was changed last year, so it is unlikely to be the route cause.

Any other ideas?

 

[Agile]

Hi

My 8 years old Baxi boiler had been giving only warm water for the last few months. I thought the issue was the secondary heat exchanged so I had it replaced.

Thanks for any suggestion.

You have not explained why its YOU that has the thoughts and then you get someone else to replace it !

The obvious answer is to get a professional to diagnose the actual fault and then fix it.

The only place to correctly diagnose a fault is in front of the boiler. You will see many on forums who make guesses and say that something is definately the fault only to become deflated when it turns out to be something else.

Tony

 

[ftual]

Hi Tony

Thanks for your post.

The last professional that attended my boiler for the same issue left it non working: he didn't reconnect properly the control PCB and was unable to diagnose a problem with the diverter valve rod not extending far enough to trigger the microswitch. I had to do this debugging myself to put it back in its original state. Since then I would rather get the advice of a community of experts about what is wrong with my boiler before I call a professional.

Also, if I may ask, why do you participate to this forum if you believe that "the only place to correctly diagnose a fault is in front of the boiler"?

Have a nice day!

 

[Agile]

All that I can say is that he was obviously not competent to repair boilers. One wonders how you came to call someone who is so bad.

You need someone who IS competent !

The only place to 100% diagnose boiler faults correctly is at the boiler. Anything else is just guesswork. Because unsubstantiated guesses are potentially time and money wasting I dont make them.

Who guessed that your plate HE needed changing?

Whilst in over 90% of cases I know exactly what is wrong with a boiler before I arrive to fix it, there are a few cases where its something else. Either because the symptoms were wrongly described or just because there can be several different causes of a particular fault condition. Sometimes not even in the boiler.

Tony

 

[ftual]

Hi Tony

Thanks for your post.

One wonders how you came to call someone who is so bad.

Please let me know your magic formula to find a good plumber before you employ him for a job.

Who guessed that your plate HE needed changing?

It was one of the members of this forum.

Whilst in over 90% of cases I know exactly what is wrong with a boiler before I arrive to fix it, there are a few cases where its something else.

My boiler is now fixed. The description of the symptoms above are rigorously exact. Now, please demonstrate your 90% success rate by putting forward your most likely root cause for this issue.

Come on, dazzle me!

 

[namsag]

Sounds just like what happens when one of the sensors go. Boiler cycles continually
Is the heating ok . if so its the sensor by the plate heat ex