Boiler not firing up (Ideal Classic FF240)

26 Aug 2020
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United Kingdom
I have a bit of a quandry I'm hoping someone may be able to shed some light on. In a nutshell, THE BOILER WONT FIRE UP!

I have the following system:

Ideal Classic FF240 Boiler (probably 20 years old)
Nest 3rd Generation Thermostat
Hot Water Tank
Tank in attic

Worth noting: This boiler doesnt have an "always on" pilot light. When the Nest tells it to come on for CH/HW, the gas is pumped and the boiler sparks to ignite

When the stat sends the message to the boiler, I can hear a click from under the stairs (where the distributor valve, pump and hot water tank is) and a faint click inside the boiler cupboard from the boiler, as well a faint whirring sound and then nothing. Its like everything is working up until the boiler and then the final message to spark to ignite is not happening despite the rest of the system working up to that point. I know this click in the boiler isnt the ignition spark as that is louder and actually clicks twice on ignition

This issue has been happening on and off for around a year now and we're now on the third go round of this particiular problem. Whats annoying is it eventually sorts itself out after a week or 2 and then works fine again for 3 - 6 months before failing again

Previously we've called a plumber and booked in and by the time the plumber is due to arrive, it is working again and have had to cancel however this ongoing problem isnt ideal and I'd like to try and work out whats going on with it

Because it does have long periods of actually working, its confusing as to what it could be because when it does work, it works perfectly

Any ideas???
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I had the fan and PCB replaced 3 years ago. Is that about right for the fan to go every 3 years or so? It wasnt making any strange noises up until the shut off point which made me wonder whether it was something else

Especially as it intermitently works/doesnt work??
Could be the air pressure switch, they sometimes give intermittent faults
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Really good boilers, worth getting someone in that knows this boiler,
I had the fan and PCB replaced 3 years ago. Is that about right for the fan to go every 3 years or so? It wasnt making any strange noises up until the shut off point which made me wonder whether it was something else

Especially as it intermitently works/doesnt work??
Would expect fan to last longer than 3 years.As said,intermittent could be pressure switch sticking,and as said good boiler,worth preserving.
I did have an air pressure switch replaced on my (almost identical) boiler. It's an FF250 and was fitted in 1996 when the house was built.

The symptoms of the failing air pressure switch were ... when calling for heat the fan started up but just kept running with no ignition - this lasted for anything up to a minute or so and eventually it would fire up. It didn't happen every time, it started off as what you'd call an intermittent fault, but gradually got worse over time. I have a tame engineer who looked at it and reached up behind the boiler and got hold of the flexible rubber tube that connects to the air pressure switch and gave it a squeeze and it fired up.
The act of squeezing the tube always got the boiler to fire up, but, clearly, it needed fixing and a new air pressure switch did fix it.

It's been fine ever since.

It's had a fan or two over time and I'm keeping fingers crossed the present one keeps going. It's had a PCB and a gas valve too.

When I moved in, 15 years ago, it hadn't had much attention and it didn't take long before it started kettling. Over the period of my ownership it's had several drain downs and treatments with various boiler and system cleaners and preventative treatments and it's had a Spirovent magnetic filter on the system for a few years. Like i say, fingers crossed it keeps going as I'm undecided what (heat only) boiler to replace it with. I'm leaning towards Intergas but I guess Baxi would have to be a consideration too - Less keen on Vaillant and even less keen on WB.
Please dont mess around with the air pressure switch, it is there for a very good reason, it is a vital safety device, should only be worked on by a pro
Update on this guys

I had a heating engineer in today and he thinks hes diagnosed the fault to be the PCB board. Apparently on the PCB where the fan relay is, theres a scorch mark so it would look as though the relay that tells the fan to turn on is knackered. He echoed previous sentiments on here that the boiler is good quality and they are relatively easy to work on and hes worked on a lot over the years, so feel as though we are on the right track...all will be revealed when the new PCB board goes in. Hes going to get a quote and come back to me but looking online it appears they are around £120 so I'm guessing in the region of £200 ( to supply and refit with any luck

Updates to follow if this cures the issue!

The PCB board has now been replaced and she is alive once more. The engineer also put a new seal on it as well so all good. Bit annoying the PCB was the culprit seeing as I had that replaced 3 years prior but hey ho

Total price was £90 for initial visit to fault find then a further £276 to source parts and replace. All in all over both visits he was here around 2.5 hours for a total cost of £366

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