Baxi Combi instant 105he

[obseen16]

Hey guys,
went to check out the above boiler. symptoms - heating is perfect but no DHW.

closer inspection revealed the diaphragm for DHW is damaged and isnt pushing the pin into contact with the mico switch (with the black & White wires). That part was simple enough to figure out BUT when i bypass the diaphragm (by running the hot tap and manually pushing the microswitch in with a multimeter probe end the boiler fires and luke warm water comes out the tap. the weird thing is the CH return pipe starts to get hot when i did this. is this because of the split diaphragm? or am i missing something? never seen this before, i thought maybe a diverter valve problem but if that was the case the heat would go down the flow pipe not the return?

Does any one have any ideas on this as their technical guy didnt have a clue. :6:

thanks guys.

 

[Billy Bob Bob]

diverter has failed completely ,or plate heat is blocked

 

[obseen16]

**UPDATE**

Thanks for the help there Gas man, i changed the diaphragm this morning, it had a rather large split in the side, put it back together and fired it up expecting luke warm water (i was practicing my look suprised face all last night to). turned the hot tap on and it ran perfectly. i left the tap running for 5 mins expecting it to go luke warm or overheat and lock out but nothing, i felt the return pipe and the flow pipe and they were stone cold. i really cant see how a DHW Diaphragm could be all that was at fault but hey maybe it was.

im pleased it was only the diaphragm but a little suprised at the same time. i really was thinking the plate HE would have to come out. happy days. 😀