Baxi Combi instant 105e: RIP?

[gavben]

Got a Baxi Combi instant 105e, installed ~6yrs ago. Had a few problems over the years with going over pressure & venting through pipe to outside, but fixed & okay for last ~2yrs

As weather got colder ~6wks ago, noticed heating would only reach the first ~2 radiators. Had two different heating guys out who couldn't work it out. Cleaned & flushed the radiators, but no success.

Another guy came 2 weeks ago and diagnosed a stuck diverter valve. Came back a week later to fit it & suddenly all the rads were hot. Next day, I reconnected a rad in the kitchen & topped up with inhibitor & suddenly no heat to most of the rads. Got the guy back out & he thought the PCB had gone (diverter valve seemed not to be getting controlled properly).

Boiler seems to be trying to run all the time, even when switched to water only & with taps off or when timer is off. None of the panel lights work (except the green "power" light bottom left).

Heating guy is now off sick, but one of his colleagues came & tried new PCB. Did not fix the problem, so he removed & arranged to return PCB, but said we'd need a new boiler.

Got a frozen wife & kids, and we're in the middle of building an extension that we need to move the boiler into (~end year). Replacing now & then moving it a few weeks later would seem a nightmare as well as ruinously expensive.

Anyone got any ideas?

 

[kevindgas]

get the whip out and beat the builder to get on with the build
buy a few cheapo 2kw heaters from homebase/bodge & quick!

the boiler isn't worth spending any more money on if you are getting a new one.

 

[gavben]

Thanks. We were originally hoping to move the boiler rather than replace, but it seems like it's on its' last legs

 

[powell30]

Rubbish. Get someone in who knows what they are doing. Define what you mean boiler keeps trying to work all the time......but only the green on light is lit?

Does pump run? fan run? ignition attempted?. The issue is diverter related! Has the electrical diverter head been checked? Micro switches at front of div valve been tested?

 

[gavben]

The only light on the panel that works is the power light. The most recent guy changed the diverter valve head, but it would not move when heating kicked in (hence trying a new PCB).
The boiler is firing briefly, going on & off, whether the heating is turned on or off, timer or constant. Pump runs, fan runs & boiler ignites. The first 2-3 radiators are hot, but the water does not get circulated. Hot water is fine.

We are in Cambridge, can you recommend someone who does know what they're doing?

 

[powell30]

Take off the electrical head on the DV off and use something to push down the pin, then turn on boiler and see if it stays lit and your rads begin to heat up properly. Then get back on here and post the results......was the hw differential changed at the same time....top right of dv?

 

[gavben]

Take off the electrical head on the DV off and use something to push down the pin, then turn on boiler and see if it stays lit and your rads begin to heat up properly. Then get back on here and post the results......was the hw differential changed at the same time....top right of dv?

Yes to the first bit, the guy who name in showed my wife that pushing the DV pin would get the water to the right place. The head was not getting "told" to move it. The diff was not changed.

 

[Corgigrouch]

Might be worth just checking that the piston that triggers the DHW microswitch isn't sticking out causing the boiler to permanently call for hot water, though I would expect the display to show more info if this is the case... Just remove the circlip holding on the micro switch and pull the switch free and see if the boiler switches off... Had a similar thing a few months ago... Worth a try

 

[gavben]

Just had a go at both suggestions above. On pressing the diverter valve plunger, the boiler stays on & the whole system heats up. With it released or with the head connected, it fires for ~2s, then shuts off. Certainly seems as though the diverter valve is not getting the required control.

I also tried taking off the dhw microswitch, to no great effect.

If it's not the valve or the controller board, what inputs to the controller could be screwy to stop it triggering the diverter valve?

Sorry, I may be thinking too much like a scientist & not enough like a heating guy.

 

[Agile]

Has anyone checked the sensors?

It might just be continuously trying to preheat the water store.

These ar recent and totally repairable boilers as long as you have someone who can repair boilers!

Tony