Valliant GB 242EH - No Ignition

Yorkie59

Today, a traditional rest day & one that I would normally spend watching Football & Snooker on TV, the combi-boiler decides it doesn't want to light.
It is controlled by Horstmann Coronet 425 controller which appears fine.
Water pressure shows 1.4 bar. Neither the demand from the Heating or from the Hot tap will get ignition.
The controller seems to have a fairly steady orange light in the Top RH corner. The Boiler does NOT have a RED light on to show failed ignition.
I have reset - and still no start up. Checked the two BS4265 2Amp fuses and they appear OK on the multimeter (0.1 ohms). The other BS4265 fuse is 0.16Amps and has a resistance that shows as "01.2" Ohms. This surprised me because of the leading zero on the digital display. (Just tried a 3Amp household fuse & got 00.2 so the leading zero is a pink hallibut, sorry red herring) 1.2 Ohms is not high but with such a low rating, was higher than this engineer expected.
We have a very poorly 16 year old with a terminal condition.... the last thing we need is no central heating :cool: .
Any ideas, thoughts, suggestions welcome. Typically, we had to give up our 3 star coverage due to cash flow problems and a call-out fee is out of the question without a loan.
Thanx in advance - all feasible ideas welcomed!

Yorkie59

I should say also that holding down the black (ignition/reset) button does NOT create any sound in the bioler. The controller (orange) light actually could be flickering - but very fast

Canucklehead

Hi... can you tell if the fan is running?

Corgi Guy

Yorkie59

There is a noise -- I'll pop down & try & explain what it sounds like.

I should say also that holding down the black (ignition/reset) button does NOT create any sound in the boiler. The controller (orange) light actually could be flickering - but very fast.
There is NO ATTEMPT to light the gas on starting the heating. On odd occassions in the past there may have been a few attempts followed by the failed (RED) light coming on. I don't hear anything on (trying to) start up. Likewise, hot water which normally demands a light up, doesn't do anything.
Is there perhaps a pilot light that has gone off? (I can't see one) - and without the pilot, the gas will shut off - or it did on another Valliant I had in Essex. Am I missing something obvious here (household electric, gas & water are all working AOK elsewhere).

espresso

Air pressure switch? see here

Try to locate a manual on-line to download which may have a fault finding flowchart.

Yorkie59

There is a steady low drone from the top of the unit when the black switch is moved from 0 to 1 (ie heating switched on). Then a click and nothing else. Yes this is the fan running

Canucklehead

Hi...could be blocked venturi, water in air pressure switch tubes, the air pressure switch itself or the fan might not be achieving maximum speed because bearings are sticky/failing. Try posting on https://www.diynot.com for additional thoughts... gas4you on the P&H forum is the resident Vaillant expert there.

HTH

Corgi Guy

Yorkie59

OK - I have now located the Installation and Servicing Manual and found Chapter 15 Fault Finding.
New information - which I should have known - the red neon in the Main (red) switch does NOT light up when the switch is moved from 0 to 1. Not good news methinx. Heating startes this am and went off around 10 o'clock according to OH. Since controller was set to All Day - this should not have happened.
I've checked the 2A fuses so either I have no 240V or the Main Switch Circuit Board could have gone. I recall the APS was an issue around 5 years ago (when we had cover) and so may also be again.
I'll keep you posted.
Thanx for help to date

Yorkie59

OK - more info on the APS. Carried out the Gas Soundness test in para 11.6 - the one where you fit a hose to the Test Point (TP) and suck - the main burner fired. As you suck on the tube you hear a distinct click as the APS is operated. Now, I'm starting to recall a day many moons ago when I chased a fault on a Ford Cortine Mk2 without checking a bulb. The red main light bulb not coming on can't be taken as read - if u see what I mean.

espresso

Sounds like you are getting warmer and need to source this part. Best of luck.

Yorkie59

I think I am safe in saying that the fault is now isolated to one of the four suggested by Canucklehead - not sure it is the APS yet - blocked venturi & water in the APS pipes are fairly quick checks after I get the lad to bed that is. At least he won't get too cold that way.