CH Boiler won't light

[Bob]

My boiler (Vaillant VC GB 242 EH) has suddenly decided to stop working (waits until it's getting colder of course).

When the hot water / heating is demanded, the pump and flue fan run, and the ignition starts sparking, but it just won't light. It doesn't give up either (like it did one time when the pump had failed). The ignition just keeps tick, tick, ticking until I turn it off.

I tried loads of places in the yellow pages, but they are all apparently too busy - even the ones that claim "engineer in one hour", so I was wondering if there is anything obvious I should check while I wait for them to run out of other work...

Also, if anyone knows of a site where I could download the manual that would be handy - I can't find mine anymore. It must have sat next to the boiler for at least 3 years - now I need the damn thing it's not there :-(

Mal

[Des Higgins]

I do not think this helps but ...... something like that happened me with an oil fired boiler 7 years ago in an old house. There was a small red (or orange) button near the boiler. It was some kind of reset button for the ignition. It does not sound like this is your problem though if your ignition is sparking. Is yours oil or gas?

[Bob]

Gas.

If the pilot fails then a light comes on and I have to push a button to reset it. This hasn't happened. It's just sitting there ticking away without lighting :-(

[Set Square]

Sounds like gas isn't getting to the pilot. Silly question - I suppose that the gas hasn't inadvertently been turned off?

Looking at the diagnostic chart for my similar Baxi boiler, for your sort of symptoms it points to the pilot jet being blocked or the pilot solenoid not working. If it's like mine, it is a 2-stage process. The spark lights the pilot - and some magic trickery to do with flame ionisation, which I don't understand, stops the sparking and turns on the main gas valve.

When it's doing this trick, can you smell gas if you go outside by the flue?

[Bob]

The gas is on - the cooker is working just fine.

I'll try having a sniff around outside. I thought there might be something blocked, but when I took the cover off the boiler, I couldn't see an obvious way in - and without that manual I didn't feel like guessing!

Mal

[Set Square]

Yes, but is there a separate tap near the boiler - or inside its casing?

[Bob]

Not that I've ever seen. I'll have a look when I get home.

Mal

[Jimbo]

Were it mine--I'd give the burner plate a good brush over to clear the orfice's and a good vacumn of the gas inlet air hole and try it again. Good luck. Jim

[chris French]

In message , Bob writes

I've had similar problem before with my boiler (not Vaillant). AFAICS the clicking noise isn't the spark as such, but the sound of the park generator, problem was in my case a spark wasn't produced at the electrode.

I have resolved this in two different ways:

1. The seemed to be a loose/dirty connection between the cable and the electrode - cleaning it up and squeezing the connector on the wire gently with pliers has sorted this problem.

1. The electrode itself seemed to get a little bit of contamination on it - possibly shorting it out. I took it out cleaned it up and it was ok afterwards.

I've got spare one in stock now, for when it goes again - I'll just replace it.

Access to the electrode was easy enough, just remove the front inner casing of the boiler

[Bob]

I would if I could work out how to get in there without breaking stuff!!! Looks like I'll be playing hunt-the-manual again!

[mike ring]

"Bob" wrote in news: [e-mail]:

Is it possibly the thermocouple? I don't know anything about Vaillant boilers, but most of my dfailures have been a failed thermocouple turning off the gas, even though the pilot is alight, because the boiler thinks it isn't.

I now keep a univeral themocouple handy.

mike

[Cicero]

=============== This sounds like the unusual problem I had a few weeks ago, although with a different boiler.

When the fan starts it should open an air valve which in turn opens a gas valve and the pilot then lights. One of the two tubes from the fan housing to the air valve had become blocked. I cleared the blocked tube and the boiler then fired up immediately and has continued to work perfectly.

IF your boiler has a similar arrangement you should disconnect each pipe in turn at the air valve end and try blowing through to test if they're blocked or clear. If you find that there is a blockage then clear it carefully. Since I didn't know what size the hole should be I removed the fan assembly to clear the hole - about 3/32" so care is needed. It's also possible that the actual air valve is faulty but it's worth a quick check as describd above.

Of course, ignore all the above if your boiler is completely different!

Cic.

[Set Square]

Doing a quick Google on Vaillant, it appears that you can download manuals from

you have to register first.

[Andy Dee]

From what you have said, it sounds like a control circuit fault. For ignition to happen, both pump and fan (if it is fan assisted) have to "prove". The boiler should definately NOT sit there in ignition mode for longer than 30 seconds. It should "lock out". I used Vaillant service for mine recently, they offer a fixed price callout and fix. (was £75) Try:

[raden]

In message , Bob writes

No gas igniting at all ?

Then it's either the gas valve or the Flame Supervisory board

(until Ed comes along and suggests something else)

The first thing to do is test the resistance of the solenoid on the gas valve. If there's some finite resistance (I forget exactly how much (about 5k IIRC)), i.e. not open circuit, then I would suspect the FSB (10-0542 or 10-0555) in which case look at my site

The pcbs are in the grey mazak box in the middle at the bottom of the boiler and the front is removed by undoing the four screws holding it in place. Also undo the nut holding the reset switch to the front cover. The rest should be obvious from visual inspection

If the reset button's not pinging out, (bimetallic strip timer in the reset switch) I would suspect the FSB

I have one somewhere

[raden]

In message , Set Square writes

The reset switch should ping out if the FSB doesn't detect the flame within a certain time period

[raden]

In message , mike ring writes

Electronic ignition

[raden]

In message , Cicero writes

No - if it's sparking, the electronics has sensed that the PSW has been activated

[raden]

In message , chris French writes

Again ... the OP indicated that the reset switch wasn't popping out

[chris French]

In message , raden writes

Is this relevant in this case?

I had no problem with a reset button popping out/needing resetting either.

The symptoms the OP described were exactly the same as mine, which I resolved as I described. I've no experience of the OP's boiler though so of course things may be different - I was just offering my experience