Worcester Bosch Combi Ignition Lockout

[Dan Robinson]

Call a professional.

 

[cowboy_diy]

Thanks Dan for your reply.

I've already made that call which left me with a £400 quote :/

I'm only looking for some help to locate and replace the flame sensing electrode before I cry and pay for the new boiler.

 

[Agile]

That's not very informative!

What was it you asked for to get a £400 quote?

Generally BG would be cheaper.

And probably Worcester themselves.

Tony

 

[cowboy_diy]

Hi Tony

I asked for the ignition lockout problem to be fixed, they quoted £400 to replace the pcb and flame sensing electrode including parts and labour. The engineer made a call to WB technical helpline and explained the symptoms and they probably said pcb OR flame sensing electrode.. so he quoted me for pcb AND electrode.. one of which will fix my problem.

I checked flame sensing electrodes are cheaper in price so thought I'd give them a go. Reading some forums people said it's am easy job so thought I'd get some help.

That's where I'm coming from.

 

[Agile]

Yes, but electrodes are an item that should only be replaced by a Gas Safe registered engineer and not a DIYer!

But any competent engineer should be able to check/test them anyway.

If the guy you called had to call Worcester, then he clearly does not have any diagnostic skills of his own. There is only one place to diagnose boiler faults and that's in front of the boiler!

Tony

 

[muggles]

Thanks All.

Ollski, Is it a DIY thing to replace the gas valve? I'm not a boiler expert but I do quite a lot of diy.

Please can someone also point me to some help in terms of how to replace the flame sensing electrode. The manual doesn't have anything in this regard.

Thanks.

Thanks All.

Ollski, Is it a DIY thing to replace the gas valve? I'm not a boiler expert but I do quite a lot of diy.

Please can someone also point me to some help in terms of how to replace the flame sensing electrode. The manual doesn't have anything in this regard.

Thanks.

No, definitely not DIY to replace the gas valve, or the flame sensing electrode, or anything else inside the sealed combustion chamber

 

[cowboy_diy]

Thanks Tony and Muggles. It's clear to me now that I shouldn't be doing it myself.

The reason I was wanting to replace flame sensing electrode first was because I observed that even when the flame is on (before ignition lockout happens) the spark electrodes keep on sparking.. that made me think that the sensor is possibly not recognising that the flame is on and hence the spark electrodes keep on sparking, and since it cannot detect the flame even further it disrupts the electricity to the gas valve which triggers the lockout.

 

[Agile]

Some boiler designs stop the spark immediately the flame is detected. Others don't!

If the flame is not detected within a fixed time of about 5 seconds the boiler assumes the flame has not lit and ceases powering the gas valve. That sequence is controlled by the PCB.

You need someone with diagnostic skills who is not what we call a "parts changer".

Tony Glazier

 

[ollski]

cowboy in your first post you said you had exactly the same fault as the op whose boiler was intermittently failing at random points so I say gas valve. now you say its failing to rectify which means pcb (poss. f/s electrode / reverse polarity). This is why its better to call someone in.

 

[cowboy_diy]

Thanks all for your help and useful comments pointing me in some direction as to what could be wrong.

I ordered new spark electrodes, gas valve and pcb thinking some combination is ought to solve the problem, and got someone in to do this;

Replace the spark electrode - issue persists.
Replace the gas valve - issue persists.
Replace the pcb - Yayyyy! The issue of ignition lockout is fixed but now the central heating is continuously on despite setting a very low temperature at the thermostat The gas engineer left saying the pcb is still faulty which is causing the CH to stay on and needs to be replaced again.

Took hours of reading to find out that the gas valve pressure setting on the pcb can cause this, confirmed from the service manual as well.

Opened the pcb and it was set to max ..arghhhhh! Set it to normal and happy days!

Thanks all, you are all awesome!

 

[FiremanT]

Thanks All.

Ollski, Is it a DIY thing to replace the gas valve? I'm not a boiler expert but I do quite a lot of diy.

Please can someone also point me to some help in terms of how to replace the flame sensing electrode. The manual doesn't have anything in this regard.

Thanks.

TO: OP Cowboy-diy
if you read the site rules (I know, who does?) you will see we are not allowed to give specifc gas work advice.
Probably because of the risk of cowboys reading it
Changing a gas valve is not a diy job.It needs setting up

 

[outy]

I had a similar problem with my old Worcester 35cdi. It ignited properly but after a few seconds it would start intermittent ignition sparks when the flames were clearly on and the sensor was in the flames. As everything warmed up the additional unnecessary sparks became more frequent until an ignition lockout occurred. After a reset you could start again but it rarely stayed lit long enough for a shower. A heating engineer diagnosed a pcb fault but said that the boiler was old and obsolete, a new pcb was not available and as I was planning a new heating system in the near, but not immediate future I should just bring my plans forward. All reasonable advice. However I saw a firm in Cowgate, Newcastle offering guaranteed boiler pcb repairs and as I was local too them took the board to them, they inspected it, confirmed a fault and fixed it, two large capacitors were out of spec. under load. It was worth it to me to get the boiler running for a few weeks until the planned upgrade.
Chris

 

[muggles]

I had a similar problem with my old Worcester 35cdi. It ignited properly but after a few seconds it would start intermittent ignition sparks when the flames were clearly on and the sensor was in the flames. As everything warmed up the additional unnecessary sparks became more frequent until an ignition lockout occurred. After a reset you could start again but it rarely stayed lit long enough for a shower. A heating engineer diagnosed a pcb fault but said that the boiler was old and obsolete, a new pcb was not available and as I was planning a new heating system in the near, but not immediate future I should just bring my plans forward. All reasonable advice. However I saw a firm in Cowgate, Newcastle offering guaranteed boiler pcb repairs and as I was local too them took the board to them, they inspected it, confirmed a fault and fixed it, two large capacitors were out of spec. under load. It was worth it to me to get the boiler running for a few weeks until the planned upgrade.
Chris

Given that this thread is 9 years old, I quite expect that they're sorted by now

 

[outy]

Yes, I knew that I would be unable to help the thread starter but when I was problem solving my issue this thread was the closest that I could find describing my situation. As I'm not up to making a YouTube video I thought it an appropriate place to put a possible solution to the problem for anyone else doing a internet search of the symptoms. I love forums, although old tech they are quick to scan, few adverts and some knowledgeable contributors, the only frustration is when an originator of a problem doesn't give the outcome, which is usually that they sold the car with the fault. diynot is often the best source for home related problems.
Chris