Baxi 105e not firing up

[leego]

please will somebody help?
i have a Baxi 105e which is not working at the moment. It is only 16 months old !
originally it started to cut out with the neon warning light above the 50 degrees flashing which suggests problems with fan or external flue.
the installation manual says to got to section E and check external flue, pressure switch, and venturi. all of these have been checked and replaced.
the boiler now fails to fire up at all when turning HW & CH and the above warning light comes on after about 5 seconds every time. this is the only warning light that comes on if this helps so we assume we dont need a new pcb.
can anybody suggest anything else to try who may have had similar problems.

 

[gazthepottertonengineer]

check venturi again as this may have melted if it has dont just replace as there will be another reason why this has happened normally due to overheating possibly down to pcb

 

[leego]

the venturi we took out was not damaged at all but we still changed it anyway.
apparently there is another venturi down by the cold water inlet but cant see that this would be related - nightmare to remove.
everything seems to point to the pressure switch as the one we changed it to was second hand. so are gonna try a new one tonite. fingers crossed as we dont know what to try next without forking out for a new pcb when the guide doesnt indicate that this would be the problem.
any other ideas please ????

 

[Paul Barker]

The other venturi is Baxi's way of flow sensing domestic hot water demand and is a red herring to your situation.

You would need to check if pressure switch makes necessary contact if it does you are probably looking at pcb but I'm not a potty engineer so don't take my word. If pressure switch doesn't activate you would want to re check the venturi and the flue and put a u guage on the pressure switch tube connecting points to measure fan pressure and check agains manufactrurer's instructions, if they are within ratings buy a new pressure switch, if they are not buy a new fan (only if you are absolutely sure all ways are clear), advance to Old Kent Road and collect 200 as you pass go..

 

[leego]

tried new pressure switch and no joy.
we can only put it down to pcb now as everything else has been checked and seems ok.
our only worry is why does only one warning light come on for check fan/flue above the 50 degrees ?
but all else seems to point to pcb.
any more thoughts - getting colder and more desperate now.......

 

[leego]

just got thro (eventually) to baxi tech support.
they have suggested that it could be the spark generator if there is power to it. the pcb must be working if there is power to the spark generator.
thats the next thing to check.
does this problem sound familiar to anybody ?

 

[Paul Barker]

If it doesn't try to spark you have to check for power to it, if there is power to it then it is the spark generator, Baxipotterton will tell you what readings to expect where. If no power to it then sounds like pcb.

Hopefully gazthe potty is about.

 

[gazthepottertonengineer]

tried new pressure switch and no joy.
we can only put it down to pcb now as everything else has been checked and seems ok.
our only worry is why does only one warning light come on for check fan/flue above the 50 degrees ?
but all else seems to point to pcb.
any more thoughts - getting colder and more desperate now.......

if it was spark generator then the falme failure light would be coming on i think its the first one above the 10 degrees its obviously not making the a.p.switch and thats why that light is coming on check your flue is definately ok no blockages etc

 

[leego]

cheers for the help but still no joy. tried a new pcb last night but bloomin blew a fuse when we tried it ! possibly a dud one so may try another.
we checked power at pcb to spark generator and there seemed to be no reading which suggests pcb ? power. air press switch seems to be ok as power everywhere there should. we have also had the flue completeley out and nothing there.
just seem to be goin round in circles..............
is there anything else that may be obvious that we are missing ??????

 

[gazthepottertonengineer]

id give up mate best bet is to call Baxi out £220 includes all parts labour and vat and you get a full years warranty to boot call 08706 096096

 

[leego]

success - was the pcb. now fully working.
only one more question. before we had the problem when temp controls were set to max the water and rads were too hot to touch. but at the moment they are just hot (only get up to 60 degrees on the led). is there any adjustment i can make to increase the temp on water and rads back to higher temp (i.e get back up to 80) ???
is it something to do with changing pcb ? must be somet simple we havent put back to normal. (darent ask my plumber as he is sick of me)

last one i promise .......

 

[Paul Barker]

There may be two presets on the pcb but you would have to ask Baxipotterton which is which.

A preset it the correct name for a small variable resistor adjusted with a fine tool.

 

[leego]

thanks mate you have been a legend for your help.
will give baxi a ring to talk us through it.
unless anyone knows extactly where they are ?
cheers

 

[andsam]

You have put the control knobs back on to the pcb wrong . Event though it feels as if you are turning the knob it isnt turning it fully on the board. Try refitting the knobs (done this myself) I have had the same prob with the pcb. On mine when it warmed up the pcb kept dropping the power to the fan so the aps would break.