Potterton 30He hot water intermittent fault?

[fingertight]

Can anyone point to possible cause on hot water issue on a potterton 30he.

It is an occasional fault, when it happens the following occurs:
when hot water is drawn off, the fan kicks in but there is either no ignition attempt or the ignition is delayed by upto 2 mins? so you may just get cold water out or wait ages for hot water...

other times hotwater fires up straight away but then goes cold..or hot and cold. Hot water control knob is set at around 40 to 50c but the hot water can come out very hot?

When the fault occurs there is a red flashing light on the 50c indicator which is also located above a fan sign (but I think the fan is fine, like i said...fan can kick in but no ingition attempt)? as its only intermittent I would be glad to leave it (can of worms) but im sure you guys will have some good pointers!!

 

[ChrisR]

Both are standard faults.
Intermittent starting up is a dodgy switch, around £15, but you'd need a Registered installer to fit & test it.
Outside chance it's the circuit board, - which will go eventually.

Hot/cold cycling is usually due to dirt in the system. Short term fix is to clean or replace the hot water heat exchanger. How short is short? How long has the boiler been in? It's likely to recur at about the same interval. So if it's 6 months, get the system cleaned. If it's 6 years, it's different.
Could also be a temp sensor, less likely and easy to test.

 

[fingertight]

Thanks for the tips Chris, I am registered but I thought i'd tap into the knowledge thats overflowing on this site cause I don't like touching things when It could be one of many issues?

When you say switch what are your referring to?

I don't think its a temp sensor as when I was there, it happened, and the fan kicks in but there is no ignition sequence..no attempt to spark for around 30 - 40 seconds then suddenly it will spark and its all ok.

Then when I opened up the hot again, it fires up fine, then after 40 secs or so it goes out, then fires up again and gets really hot then goes cold (which would point to poss plate to plate?)

Other times it comes on as norm, then goes cold for 2 mins? client said the other day it didn't work all morning (until 12 noon)....my instinct tells me its the board?????

 

[picasso]

I would be looking at the aps, blocked tubes, venturi and is the flue clear, is the boiler a performa ?