Vaillant F28 Lockout... what could it be.

[hardnut]

My Vaillant Turbomax 837e is 10 years old. Suddenly, I start getting F28 (ignition / no gas problems) fault code. It is an intermittent fault. But now is tuning the boiler off for most of the day. I have had 2 boiler engineers look at it; who have in turn talked to Vaillant Tech support. All of these guys give conflicting advice. They have replaced the board. They have replaced the gas valve. They have changed the ignitor (spark plug).

Having taken the front off the boiler, with the ignition sequence running, they held a match in the gas chamber. And it did not light. So you would think this is a 'no gas' problem? Likewise they could see the ignitor sparking. Furthermore; they ran a 'live' check and by hitting the fault code buttons, and according to the Printed Circuit Board, the gas valve opened and shut. (d30 = 1; =0) Still not working.

To make this more confusing, the boiler occasionally fires up in the morning. Finally I have discovered the following things.

1. Vaillant Tech Support can be reached on 01634292392 option 3. This service is only for heating engineers, but they can give helpful advice to joe public. Note avoid their customer helpline. (option 1) It is 60p per minute and totally useless.

2. When buying parts for Vaillant call their parts line and confirm the exact part number. We were sold 2 wrong gas valves and one wrong ignitor by various plumbing shops around London. Parts are on: 01773 596615. Note some places seem to sell reconditioned parts. Particularly PCB boards. And call at least the top 3 suppliers for part prices. Vaillant do not specify a RRP; letting plumbing outlets set it on their own. A PCB ranges from £220 to £110!

3. Advice: Well I have been told that... the Printed Circuit Board never creates an intermittent fault. Always is the cause of an intermittent fault. That the gas valve is never the cause of an intemittent fault. Is always the cause of the intermittent fault. That the 837e had a known problem with the gas valve. And that three years ago Vaillant changed their method of manufacture because they caused intermittent faults. That the only other thing it could be is low gas pressure.

CONCLUSION> has anyone any other ideas? I have enjoyed my time with the Heating Engineers. I notice on this blog sometimes they get the hump, with folk like me trying to diagnose the problem. Both my engineers were good. They cost so much cash. But it struck me that they were working only on a process of elimination. Rather than diagnosis. Are there any other tests; to see what it is. Perhaps like putting a multimetre on the board to see the voltage supplied to the Gas Valve? Thanks in advance.

 

[Agile]

Well if you enjoyed your time with those people then you should be happy!

But you should have called someone who offered a no-fix no-fee and diagnoses the problem first and then fixes it.

A fixed price repair with British Gas is about £200 and a better option than employing parts changers with no diagnostic skill. They also often just change parts but at least you are not paying for their mistakes.

But I see that you have been buying parts. A proper boiler engineer will buy the part and fit it. You seem to have chosen parts changers ( perhaps because they were cheap? ) and it frightens me that you may even have called people without paying them to "give a quote" and then changed the part yourself. To avoid that type of customers I ALWAYS charge to diagnose the fault.

Do I know whats wrong with your boiler? No, of course not, because I have not seen it or done any diagnostic checks on it. Nor do I make guesses either!

Wait and some of the regulars will be posting their own guesses on here!

Tony Glazier

 

[hardnut]

Hey thanks for the expert advice. In fact what happened was this. The only Heating Engineers I could find, worked this way. 60 per hour. You pay them to turn up. Then you pay them 60 per hour, to diagnose. And on top of that was parts. In fact I only found all this out because they bought parts and they would not fit. So I talked with Valliant; and that is how I figured out to quote the part numbers and to shop around. Secondly, they were reluctant to talk to Valliant, so I ended up mediating. Which is how I found out that it was either the ignitor (they changed that) board (they changed that) the gas valve (they changed that) or... and I only discovered this today. The Air Pressure Switch. (we have't changed that yet!!!)

I would never add parts to a boiler. But I do find it useful to get on the phone and figure out the prices. My heating engineers seemed remarkably ignorant of the costs.

But my question Tony is where in London do we find people who are expert with Valliant? Who turn up and diagnose and quote before the fees start? My experience is very common. How do we find people like you?

By the way. On Valliant's website is a list of certified Heating Engineers. First one I called just tried to sell me a new boiler!!!

 

[45yearsagasman]

Quote:- Wait and some of the regulars will be posting their own guesses on here.
Arrogant or what? Include yourself amongst that.

 

[Agile]

Hey thanks for the expert advice. In fact what happened was this. The only Heating Engineers I could find, worked this way. 60 per hour. You pay them to turn up. Then you pay them 60 per hour, to diagnose. And on top of that was parts.

But my question Tony is where in London do we find people who are expert with Valliant? Who turn up and diagnose and quote before the fees start? My experience is very common. How do we find people like you?

By the way. On Valliant's website is a list of certified Heating Engineers. First one I called just tried to sell me a new boiler!!!

If you engage people who charge by the hour to diagnose faults then its in their own interest to take a long time and get it wrong.

Thats why I always charge a fixed price to diagnose a fault.

The manufacturers list engineers primarily to install their boilers. As Vaillant have their own engineers they would not want to to list people to do repairs.

If you want a boiler repaired then call someone who specialises in repairs and ideally someone who charges a fixed fee and particularly a no-fix no-fee. Vaillant do fixed price repairs as well for about £230 I think.

A google search for "fixed price boiler diagnostic fee" comes up with 440,000 results. Not all me!

Anyone who wanted to contact me would find it very easy indeed!

Tony Glazier

 

[Beerlover]

When you look in to the boiler on the copper pipe above the pump, is there a black plastic cylinder with a lead about 2" long?

If so this is a pressure sensor. Assuming the boiler pressure is ok ie about 1 bar, bridge this out and does the boiler now work? It interrupts the gas valve and will give a F28 fault.

Just plucking at straws here as this fault can be a weird one sometimes.

Could be pcb, sticking gas valve, APS (but doesn't give its own fault code), faulty gas gosvernor, loom, electrodes or fan venturi.

It may be now best to call Vaillant and get 'instant cover' around £300, but they will rebuild the boiler if neccessary.

 

[Boilerman2]

The last F28 I diagnosed turned out to be a sticky Governor on the Gas meter!!

 

[hardnut]

Firstly a big thank you to all the help from the site.

Here is my overview; for Joe Public. So not you crazy heating engineers out there, but in case a civilian had the problem I had.

1. I had an INTERMITTENT F28 fault on my boiler. Over time it suddenly became permanent, showing the red light. Lock out. In the mornings it used to work. Sometimes it would work for a day. Then lock out.

The fault was a faulty gas valve. But ALSO the lead to the valve was faulty, causing the valve to blow the board as well, after a new one was installed. This meant that despite changing the valve; the problem returned. The true solution should have been change the valve. AND Change the power lead to the valve.

2. If this has happened to you, the following choice as noted by the chaps on this site are.

(a) Call a generic heating engineer.

I did this they came and changed the gas valve. The Ignitor. Problem returned. They returned and changed the board and the gas valve again. This costs a great deal of cash. The parts were over £250 alone. (The board was reconditioned.) Labour £300. They were hard to get hold of. I kept having to wait a week to get them in. They spent days getting parts. They never answered the phone. The problem was that they did not realise that one problem (the valve) was creating another (the board). And when they changed the ignitor, they installed the wrong one.

(b) Call Vaillant. Now Vaillant do the £300 instant cover and insurance. And a £280 Instant cover but no insurance and a £200 one off call out with no insurance. And a £120 insurance but you cannot use it for 28 days. I had to buy the 300 quid one. They came same day. Did a fantastic diagnosis and solved the problem immediately. That money also covers parts. All the parts for the boiler where on the van. They also just for the sake of it and for free. Serviced my boiler.

3. So firstly what type of engineer? My experience was that Vaillant, had brilliant diagnosis and as importantly all the parts on the van. So they could just switch things in and out. Secondly, they knew the boiler. And they did all the diagnostic tests to find out what is happening. They also knew all the important tips and tricks that my two generics did not. And, their work is guaranteed. That is what I should have done.

The specialist has such a great advantage by having all the parts to hand. And any number of parts being covered in the price. And his work being insured for a subsequent year. That if you are suffering a problem like this. Had I done that in the first place I would have saved hundreds of pounds. And they are RELIABLE! And they understand customer service. Heating Engineers are like dealing with British Leyland in the 70's. They make you feel you are lucky to get them. And my experience is that they either try and sell you a new boiler. Or are grumpy jobsworths, who step back from saying they don't know. Even on this site. One of the kind respondents when I said 'how do I find you?' Replied. 'People who needed him found him easy to find?' Man. No Email. No Mobile Phones number. No website. These fella live in the stone age.

4. Diagnosis help. OK. So if this is happening to you, you want to save money. This is what I also found out. Firstly F28 means it is not igniting because; the BOARD has failed. The IGNITOR has failed. The FAN has failed. The GAS VALVE has failed THE PRESSURE SWITCH has failed. THE WIRING has failed.

THE VALVE Main culprit and hard to diagnose. If you hit the i and + buttons you can switch the display on your boiler to fault finding mode. If you push the plus button until it shows 'd 30'. The boiler will cycle through '0' and then '1' as the valve opens and shuts. The Vaillant engineers and their tech support however made two different claims. One says it indicates the valve is open the other said, it only indicates the BOARD is telling the valve to open. I think it is telling you that only one side of the valve is open. NOT that the value is functional. But at least you get an indication. I had a valve cycling through the 1 / 0 cycle as we ignited. But my valve WAS faulty.

The other way, is if you remove the front of the boiler you can see directly into the gas chamber through a small opening. My HE, stuffed a match inside to see if there was any gas. So the fault could have been that there was gas but it was not lighting, because the ignitor was faulty.

Finally Vaillant, actually tested the power lead itself from the board to the gas valve. But again since this is not 'in circuit' as you test it, it is not a sure fire test. Mine tested fine disconnected, but was faulty when connected.

TIPS FOR CHANGING THE VALVE. This is crucial. YOU MUST CHANGE THE POWER LEAD TO THE VALVE, when you change the valve. Vaillant told me that the valve can blow the board. And their process is to change the Valve, also always change the lead. Again if you are using non-vaillant crew. Part no. 114189 for a Gas Valve. Quoted at £110 - £54. I don't know the part number for the cable. But I image it costs about £10. If you change one and not the other. And like me have a faulty cable. The faulty cable can blow the board. So then you get a heating engineer who changes the valve. Then comes back and changes the board.

THE BOARD. Note that the board can be blown by the valve. So probably your HE will have changed the Valve and the Cable first. But if you want to see if the board is blown, by the valve this was the test Valliant used.

First TURN OFF the power to the boiler. The test related to Gas valve failure is related to RESISTOR R203. It is below and to the left of the valve power cable socket on the board and is green. Below it. You'll see R203.

If you have a micro meter. If you turn off the power to the boiler and measure the resistance it should be between 66 - 67 ohms. You MUST turn off the power to the boiler first. If you don't you'll fry the board. Note a faulty VALVE or POWER CABLE to the valve can kill that resister.

CHANGING THE BOARD TIP. OK; so you get an engineer to change the board. First call Vaillant technical get the right part number. Mine was 0020034604. Then call at least three suppliers and get quotes on the price. Mine varied from £200 to £80. Ask also if they are reconditioned or not. (The cheap ones seemed to be). Note also if the valve has failed it can have blown the board.

THE IGNITOR: The ignitor (again only to be touched by an HE) is in the chamber. And the new ones for the 837 have two parts. One is like a spark plug. The other is the censor to tell the board if the gas ignited.

Failure can be either, no spark. So as the boiler ignites you do not see any spark. Or the boiler gas ignites but then goes out.

NO spark can be a faulty spark plug or a faulty board. But if you are changing parts change the ignitor first. It is cheap!

Or if you see it light but then go out. It is likely that the censor is broken. So that the chamber lights but does not tell the board it is alight. Causing the board to terminate ignition.

A fault however, you might not expect is that it has to be exactly in position. If they get the wrong part OR it is out by a millimetre then it may not spark. When getting the part; call the parts line and get quotes. My guys got the wrong one. And we did three weeks trying to sort that out.

AIR PRESSURE SWITCH. This I read about on this forum. Basically at the top and back of your boiler is an air pressure switch. To test it there are two paddles that supply voltage in and out. Using a micro metre set to measure DC volts; and in a range where 24 is the midpoint; So with the power on the boiler. Put one prong of your micrometre on one side and the other prong of the micrometre on the chassis. Then repeat with the other prong. This is the results. One side will show 24volts dc constantly. The other will switch from 0 to 24 volts and then back to 0 as the sequence switches through.

The switches retail at around 40 quid. And are easily changed. If it has failed; then it will kill off ignition.

FINALLY THE FAN! The only things I have no changed in the boiler is the entire wiring loom and the fan. But if you have just travelled the road to hell I have with heating engineers. By this time. You'll have called Vaillant

I hope that helps. My impression overall is go for Vaillant. It will save you a fortune. HE's called out are unlikely to come in under 200 quid. And they are forced to work on so many models that their knowledge is generic. Furthermore, because they do not carry parts, it takes time you pay for, for them to source the different parts. And even then. Mine were very cavalier about what that cost.

 

[Bunnyman]

Nice reply I am sure it will help someone however hrs is a known fault, but only on honeywell gas valves they have the diode in the lead. The part u quoted is for the sit valve this does not have the diode in the lead and hS a different lead than the honeywell .. The honeywell was fitted on the early turbo upto about 2002 then the sit valve was fitted .Vaillant prob fitted the newer sit valve an lead . The earlier honeywell diodes in the leads if failing do take pcbs out. The gas valve won't take the pc out .

Untitled

• Bunnyman
• 26 Mar 2010
• 499

 

[Agile]

Even on this site. One of the kind respondents when I said 'how do I find you?' Replied. 'People who needed him found him easy to find?' Man. No Email. No Mobile Phones number. No website. These fella live in the stone age.

Oh dear! Whilst I appreciate that you have been over charged for not fixing your boiler, I do wish that you would get your facts right!

If anyone wanted to contact ME then all you need to do is to click on my site name "Agile" and you will see my profile which includes mobile and landline telephone numbers as well as an e-mail address!

OR if you cannot do that then just put my name into Google and you wil get hundreds of results. Or Yell.com or Bt.com etc.

I know you dont read the forum rules before posting as required but if you did you would see that we are not allowed to post our contact details on directly on the forum.

Tony Glazier

 

[Agile]

Now your boiler!

The gas valve was not opening ! So your jobsworth replaced it at YOUR expense!

In reality the gas valve was almost certainly working! But its supplied with a cable which has a bridge rectifier built into the cable plug!

The rectifier can fail short circuit. When that happens, the resistor R203 on the PCB fails open circuit as a fuse would do in order to protect the PCB from an overload.

So the only real fault was probably the gas valve cable! Perhaps about £16 !

That in turn would have blown R203. Either the PCB could have been replaced or some would replace just the resistor although we are not really supposed to do that.

So some independents would have had the knowledge and experience to have repaired your boiler for little more than £100 !

You preferred to call Vaillant and pay them £300. But thats your perogative! You also called the jobsworths who relieved you of more money as well, did not fix the boiler but you still paid them. Again all your choice!

Tony

 

[Agile]

The boiler has no idea which parts are or are not working!

All the F28 code indicates is that the boiler has gone throught the ignition sequence and that did not result in a flame being detected!

There are many possible causes of that, having no gas supply being the most basic!

Tony

 

[hardnut]

Hey chaps. Good to see the debate. I have a question.

You mention that there were two types of gas valve fitted to the 837e. One; the later is the SIG. I understand you to say that this is the one without the rectifier in the cable.

Because that is the one which had gone faulty and allegedly blown the board. Is it possible for a SiG Valve's power cable to blow the board?

That is the one I had in my boiler! It dates from 2003.

The reason I wanted to document this was really just so joe public; who ran into the issues I had did not have to pay the £800+ I had to. I notice some folk say I chose to pay these guys. I think that is a little disingenuous. It would pretty hard to get these guys out and then refuse to pay them. It was only at the end of the whole saga that I figured out what should have happened.

 

[Agile]

What is relevant is when your boiler is manufactured, not when its fitted.

The later SIT gas valve does not have a rectifier bridge in the lead.

Its very rare indeed for the gas valve to fail in a way that would damage the PCB.

You also said the gas valve cable was changed. That implies you had the Honeywell valve.

If you engaged someone to repair your boiler and they dont do that job and make it work then I am very surprised that you want to pay them. They have not fulfilled the contract to repair your boiler.

 

[The831Bunny]

Sounds like it was a HW GV & the lead took the PCB out as per usual...

Group Service would have fitted the newer SIT valve, matching connection lead and the later version (604) PCB as Bunnyman said.

Let's just hope they set the jumper right