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Millsy 82

Plumbers Arms member
Plumber
Gas Engineer
Mar 18, 2012
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I have above boiler with A41 flashing up flow sensor disconnected.

So i have checked for loose wires pcb end and sensor end. I have checked the ohms on the sensor both sides and got 11k on both that was both through the wiring loom and straight onto the connections. Which says to me that there is no break in the wire as both readings the same.

So this led me to the conclusion pcb? Anthing else to check?

I'm having a stinker at the moment and have missed diagnosed 3 wrong in the last week!!!! This morning intermittent fault on burner tested capacitor and all ok pump was a bit noisy fitted new pump and capacitor is the fault!!!!!! I really dont want to have to buy and keep hold of almost £200 worth of pcb for a boiler I never work on.
 
Did you speak to technical about it? I don’t work on many of them but I’d try testing the dhw sensor and may try to replace these dhw sensor before the PCB.

Does the dhw sensor and check the filter it may be blocked. They are the 3 wire sensors it may be expecting some form of power back to the PCB.
 
It's a different sensor to the dhw sensor as it's a combined overheat and flow sensor. I am getting the same readings on the flue sensor

I spoke to ferroli they said either the sensor or check the wiring. I am not able to see 90% of the wiring as it's covered up but I would of thought that if there was a problem with the wiring I wouldn't of got the same readings. He then said if both readings the are the same then it's not faulty. Then that was all I could get out of him.
 
Are you referring to the sensor in the link?

Ferroli 39821530 combination sensor flow 100c | Wolseley

Do you test each lead individually for continuity that would confirm that the leads are not causing the issue. It would rule the sensor and wiring out leaving the pcb.

Apologies for the first post I thought you were referring to the dhw flow switch.
 
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That's the beast. I tested the resistance down them and got 11k ohms on both sides which to me says the wiring isn't a problem but I'm not 100% and tech were pretty much useless.

I was thinking dhw flow switch as well but ended up phoning them to see which one it was.
 
If everything else is fine then you’ve got to bite the bullet and replace the pcb.

Try calling technical again also see if they have any service engineers that you could speak to.
 
Usually with DHW flow sensors you are looking for a change in the DC Voltage but not too sure about Ferolli. Usually 5vdc. Is it the correct way around? If so I'd just change the sensor, as said it is more financially bearable.
 

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