Worcester 35CDi domestic hot water... odd fault.....pcb?

[farqueue]

GC number 4731139 (N.G.) Worcester 35 CDi

I am really scratching my head with this one! Firstly wherever I set the temp guage on the boiler for dhw it makes no difference not sure of the exact temp but it goes from hot to sometimes scalding hot - intermittent. If I try to run a bath the water starts to run cold after a while & then hot again in other words "Cycling" but I get more cold than hot!

I have replaced the DHW sensor - no change at all.

My theory is that the boiler is sensing an overheat situation on the dhw and that is why it is "Cycling" BUT is it doing that because a pot on the control board is stuck on full (Which would explain why moving the dhw temp dial has no effect)

Any thoughts before I shell out on a PCB? Grateful thanx in eager anticipation 😉

P.S. I repair domestic appliances not boilers but this is my own :-(

 

[farqueue]

Okay thanks to all contributors & I will report back when it is all done! I have a gas safe man to call.

🙂))

 

[farqueue]

Well guys......finaly had the heat exchanger renewed and.......BINGO! (ish) hot water is now no longer cycling, I was amazed at how little sludge was in the exchanger but it did the job....mostly LOL.

I now have the same problem in that no matter where i put the temp selector for DHW on the boiler the water stays the same HOT temperature! My nephew (Gas safe) is gonna come back and test the gas valve & voltages on PCB I will again report back 🙂

 

[diamondgas]

Thanks for getting back farqueue .... Are you sure the control knob spindle hasn't snapped, you can see them turning the potentiometer on the back of the PCB! Just second checking! You replaced the hot water sensor yeh?

 

[farqueue]

Awww! well I DID check it BUT you have planted the dreaded seed of doubt now ......I know it will be okay, but I will check again and PROMISE to own up if it's broken hahaha

 

[farqueue]

And yes I have changed the hot water sensor ;-)

 

[diamondgas]

Yep that seed of doubt .. soz for being a pain ...lol

 

[farqueue]

THIS......you will love! After several months of the hot water cycling again I did as you said Diamondgas, I checked that spindle and then thought I will just have to change the pcb.....I did that yesterday and guess what? No you don't eevne need to do you? But anyway you are right lol ....The furkin' thing is still exactly the same.

I am determined that it is fixable BUt I am now completely at a loss to explain the cause of this crazy fault:20:

 

[mike_s]

If I am not certain and suspect a major part but can not prove it after speaking to worcester technical then I usually refer it to them as they will come out for £215 including vat and if it is less than 10 years old then they will persist until it is fixed.
Better than forking out hundereds on parts that you arn't sure about and the customer will appreciate your honesty.

 

[farqueue]

If I am not certain and suspect a major part but can not prove it after speaking to worcester technical then I usually refer it to them as they will come out for £215 including vat and if it is less than 10 years old then they will persist until it is fixed.
Better than forking out hundereds on parts that you arn't sure about and the customer will appreciate your honesty.

NOW you tell me hahahaha cheers anyway Mike .....BUT .....It's MINE :banghead:

 

[farqueue]

PROBLEM SOLVED!!! Fitted a new central heating sensor....and the fault is cured!!

 

[6crazy9]

PROBLEM SOLVED!!! Fitted a new central heating sensor....and the fault is cured!!

Did this solve your hot water 'cycling' problem? or the "hot water is always the same temperature regardless of thob position" problem?

Thanks 🙂