Boiler diagnosis opinions sought - gas valve or PCB?

Hi folks,

My Baxi Solo 2 (non-condensing, automatic ignition) boiler recently stopped working. The fan runs, there is a quiet repeating clicking noise, but it does not light.

I investigated myself and observed that the repeated clicking is the sparking of the pilot light ignition spark gap. The spark is visible, but the pilot is not lighting. Occasionally it lights just a little bit then goes out instantly, as if there is a tiny amount of gas coming through.

At this point, it seemed to me that the fault must either be with the PCB (not activating the pilot gas valve) or the gas valve itself (not opening).

The gas valve (Honeywell VR4601T A1046) has a pair of terminals towards one end, and a group of three terminals at the other end (*). I guessed from the layout (but it's only a guess) that the pair are the terminals for the pilot valve solenoid. I found 240V across these when the boiler was trying to light. From this I concluded that it is the gas valve, and not the PCB, that is faulty.

To accelerate the repair process and avoid two call-outs, I ordered a replacement gas valve and arranged for a CORGI-registered engineer to visit. I hoped he would agree with my diagnosis and would be able to replace the valve using my part.

Unfortunately I was not in when he called. He bumbled around a bit, spent some time on the phone to Baxi technical support, and apparently decided it was the PCB, not the gas valve. I don't have much faith in his abilities as he apparently said he couldn't see any spark (which is definitely visible through the observation port) and thought the clicking was the valve (which I'm fairly sure it isn't). On the other hand, he is the boiler engineer and he did check various terminals etc while on the phone to Baxi.

My question: does my amateur diagnosis seem sound? Or should I trust him? As things stand, I will have to pay for a PCB and two visits if he is right (I can return the valve I bought), or a PCB, two visits and a gas valve if I am right. Alternatively, if I was sure enough that the fault is indeed with the gas valve, I could cut my losses and get a different engineer out who might agree that it's the gas valve and just replace that.

Opinions very welcome!

Cheers,

Seb

(*) picture at

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Reply to
Seb
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Not a boiler expert, but on my last boiler the pilot jet needed occasional cleaning. If not it didn't produce enough heat to operate the thermocouple. In your case if blocked it wouldn't light. If it's easy to remove have a look under a magnifying glass - it will be obvious if there's crud there.

Reply to
Dave Plowman (News)

Maybe, but it's not *that* sort of pilot, and there's no thermocouple. The pilot isn't on permanently, but only lights - by spark ignition - when the boiler needs to fire. The PCB detects that the pilot has lit (by means of flame ionisation or some other magic which I don't fully understand) and turns on the main gas valve.

If the pilot isn't lighting, it could be for a variety of reasons:

  • the jet itself could be partially blocked (the cheapest thing to check)
  • the PCB could be failing to tell the gas valve to feed the pilot
  • the gas valve could be failing to respond to the command from the PCB
  • there could be a problem with the spark ignition
[I expect Geoff will be along soon with a technical explanation].

I've got an older (MkI) Solo [different electronics but the mechanical bits are similar] which refuses to light if the two big screws which hold the outer casing on are done up too tightly. I can only assume that over-tightening them distorts something enough to interfere with the spark gap. It sparks away like mad - mainly *outside* of the pilot chamber - but doesn't light. Slacken the screws a bit and away it goes!

Reply to
Roger Mills

You have the valve so fit it. If it works cancel the "engineer". If it doesn't take it out and take it back.

Reply to
dennis

If I remember correctly from my Baxi Eco 80 (long gone now thank God, a beautiful Vaillant EcoTec Pro now doing the duties) you can test the gas valve by putting a manometer on the test point and watching the gas pressure rise as it opens. You can either make a manometer, or BES have them for a few pounds.

Reply to
Cod Roe

In message , Roger Mills writes

For the last time for 3 weeks ...

The Solo2 has electronic flame sensing - no Thermocouple

First question - has someone accidentally turned the main gas tap off by the meter ?, do you have a gas cooker, is it working ?

The problem sounds like a lack of gas if it's just coming on a little , the gas valve solenoid is 240v and so, if there were not sufficient volts getting there, something would be seriously over heating. The valve seat could be sticking, lack of gas to the valve or a blockage at the jet

It is ososimple to determine whether it's the pcb or valve, check whether you have mains at the pilot valve solenoid when the spark is clicking

That's it really

EK004 calls, and I haven't started packing

so

Salamat tinggal, untuk tiga minggu

Reply to
geoff

Err, isn't that what I said?

Reply to
Dave Plowman (News)

Thanks Geoff, and everyone else who has responded. There *is* 240V across the pilot valve solenoid when the spark is firing. I can also hear and feel the solenoid clunking when I turn the boiler on or off - so it is at least trying to do something. Yes, the gas supply is turned on (cooker works).

So it seems the conclusion is gas valve or blocked jet. I can see the pinhole end of the pilot jet inside the chamber. Looks OK to the naked eye but I can't get up close, and removing the injector looks tricky. Guess I could try cleaning it in situ with compressed air or an extremely fine wire (but what if it broke off in the jet?!). How would a professional clean/unblock it?

Either way, seems like a waste of money for the engineer to fit a new PCB. Guess I'll try and get a different engineer to come and fit my gas valve if I don't have any luck cleaning the jet.

thanks again, Seb

Reply to
Seb

It does have a test point, but I think it's on the main burner gas outlet, not the pilot outlet, so is no help.

Seb

Reply to
Seb

Even if I took the plunge and fitted it myself, it has pressure adjustments on it which I wouldn't know how to set.

Seb

Reply to
Seb

Reply to
Heliotrope Smith

15.8 of
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implies the valve is not adjustable.

However it does talk about doing a CO check, presumably incase they have screwed up the replacement valve.

Reply to
dennis

valve.

Reply to
dennis

Yes, indeed. And I didn't disagree - but simply went on to amplify, and clarify how this type of pilot works.

Reply to
Roger Mills

True, but these are not the instructions for my boiler. I have a Solo

2, not Solo HE.

Seb

Reply to
Seb

I bet the gas valve fault finding is the same.

Maybe they have the solo 2 on there too?

Reply to
dennis

Similar, yes. I have just found the Solo 2 installation manual via the interpart (Baxi's parts wing) website.

My conclusion is unchanged after consulting the fault-finding chart: faulty gas valve or blocked pilot injector. Am getting a different engineer to investigate next week since I don't really want to get into dismantling gas seals myself.

Seb

Reply to
Seb

In message , "dennis@home" writes

Solo 2 and Solo HE are not the same (gas valve wise)

If you don't know, STFU

Reply to
geoff

STFU. Why are you answering old threads without any useful contribution? TMH not playing with you?

Reply to
dennis

In message , "dennis@home" writes

because I've only just returned from Indonesia - the usefulness is to tell you that if you don't know, with boilers, don't give erroneous answers, you're wrong, and it can be dangerous

Reply to
geoff

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