Ideal Reponse 80 starts DHW with no water flow

[OilyRag]

***Problems with my Ideal Response 80 Combi-boiler***

Just moved into a 1950's London flat which has been left empty for two years. Boiler worked and produced HW on all taps but with poor flow. Cleaned out tap ends and found lots of debris, and flow was then up to acceptable levels.
Just put in a new kitchen and modified some of the old pipework and now the boiler starts as soon as the switch is turned.
If the taps are then switch on, the boiler remains in a safe temperature range although the water seems quite hot, as though there was no flame modulation.
When the taps are switch off the boiler keeps running until it pressurises and vents.
I removed the paddle flow switch and checked it was clean and functioning. But no difference when it was replaced.

Any ideas please?

 

[twgas]

Isolate elecs then discon the flow switch electrically, reinstate power, does the boiler still fire? If not it must be the flow switch at fault.

 

[shambolic]

Possibly dirt in the flow switch paddle keeping it in made position

 

[OilyRag]

Isolate elecs then discon the flow switch electrically, reinstate power, does the boiler still fire? If not it must be the flow switch at fault.

Very good idea. If it doesn't fire them I need t replace the switch, but what do I do if it still fires?