Worcester Bosch 28 si mk2 coventional combi

[clarkerothwell]

hi, got a combi that wont fire up for water but heating is fine (old 10 year old + twin pass h/exch)
There is a flow switch on the cold inlet, am i right in saying when i disconnect the plug leading to it (clip type conection with 3 wires to it and then to board) and run hot tap i should get continuity across two off the connections to prove it has made?

Is this the likely culprit? can it be cleaned or best to just replace?

The flow switch looks similar to the ones on the vokera range.

Any help is good thanks.

 

[gaspro1981]

The innards of the flow switch will have disintegrated you can't check it for continuity you have to check the the dc (0 to 5v) voltage across the common and the two signal wires.

Easy way to determine if flow sensor faulty is to get a new one and plug it in to wiring loom and give a good long blow through it to active the turbine

 

[clarkerothwell]

ok, thanks for the reply.

does it sound likley to be this? hot water is fine when heating is running.

 

[gaspro1981]

Quite a common problem if htg working satisfactory but no hot water when demanded however I would have expected poor/unsatisfactory hot water regardless if the htg is working

 

[clarkerothwell]

yeah flow rate is not as good to get decent hot water, untill rads are very hot.
cheers

 

[gaspro1981]

My best bet that its the flow sensor then