problems with a baxi105e instant combi boiler.

[really60]

thank you for your post bunny. i'm not quite sure what you mean by it though.

are you asking if i could swap the electric leads that go to the two sensors, as if the repair man had put them back the wrong way round?

the web site you gave was for an HE boiler, and mine is not one of those but i do have the servicing instructions for the one i've got. would your suggestion work with the non-HE version?

once again, thank you for your help so far.

 

[YELLERBELLY]

can you swap the actual sensors

 

[Agile]

If I wanted to check a sensor I would measure its resistance.

If I wanted to know if it was going o/c when hot then I would monitor the voltage across it as the boiler warmed up.

Tony

 

[really60]

thanks bunny. i haven't tried to un-plug the sensors, but if i can would you suggest i give it a try?

and thank you agile for your help. i don't have a meter to check the resistance but if i did have one, i'd certainly give it a try. also what do you mean by o/c? it's not a term i know.

 

[YELLERBELLY]

yes give it a try,o/c means open circuit,not sure how this relates to a thermistor?

 

[really60]

thanks bunny. i tried to un-plug the two leads but no-go, i couldn't un-plug them. however, while trying i rubbed my arm against the pre-heat control and turned it on. now i should explain that since the repair to the boiler i had not switched the pre-heat function on because the c/h was on and the dhw was hot enough. this situation (pre-heat off) was the same as the one last year and the year before with no ill effects.

when the pre-heat was knocked on today the boiler made a lot of strange noises but has now settled down and is working as it should. i don't know if this situation will last but my fingers are crossed.

if the pre-heat was the problem it could mean that both you and agile were right to question the sensors; i guess it's possible that air trapped in the hot water store caused the sensors to act erratically - but maybe i'm completely wrong.

either way 'thank you' to both of you for your help. i now live in hopes all is well.

 

[really60]

hi, it's me again. if anyone is still there i will describe how things went after my last post.

everything was fine until about 5pm - so for about 6 hours - and then all the lights went a little crazy. the boiler would heat to full temp then all lights would go off and the c/h sensor light would flash and sometimes the boiler would light-up again then all lights would go out for a minute or so and finally the 30, 40 and 50 degree lights would come on and after a while more the boiler would light and the whole cycle would repeat itself.
this is not the only variety of behaviour but it is typical. sometimes the time intervals varied and sometimes the number of consecutive re-lights changed but there were no obvious (to me) big changes to the boilers behaviour.

then after going on this way for an hour or so everything settled down again and at the moment it is all perfect.

while all was going crazy nothing i did made any difference. the rads could be turned up or down, water taps could be turned on or off. there is an intermittent problem that seems to go away - only to return a few hours later.

if the problem was a defective sensor that stopped working when a certain temp was reached it would, i would have thought, have stopped time and again during the 6 hours that it was ok during the earlier part of the day - as well as all the other times the boiler has worked ok for hours or days at a stretch. is there any other cause that i can try and investigate?

if it can only be a sensor (probably the c/h one) will it be necessary to just replace the plug-in electrical connector (i've figured out how to un-plug it) or will i need to drain the boiler and screw in a complete new unit? or maybe just experiment to see what's needed?

and, bunny, i don't know how an open circuit relates to a thermistor - but i suspect i'll need to in a while, so any help you can give would be appreciated.

thank you all.