HELP Vaillant Boiler not working - URGENT

[Adsibob]

We have a Vaillant Ecotec 637 system boiler that is about 7 years old. Was working fine until last night when a leak at the local water main caused Thames Water to switch the water off for the whole street without warning. It was off for about 16h. When they turned the water back on this morning we noticed our boiler wasn't working. We tried turning the tap that feeds it with water, that didn't seem to do much. When we switch it on, the blue LED screen just flashes with the word "loading" coming up on the screen, as it makes an intermittent whirring sound. It doesn't progress beyond this and just keeps doing that until we switch it off. No actual error code, nothing in the trouble shooting area of the manual.

 

Any ideas?

[ProDave]

Turning the WATER off would not normally stop a system boiler.  You would of course get no hot water out of the tap.  Did the electricity go off?  did you turn anything off?

[Adsibob]

25 minutes ago, ProDave said:

Turning the WATER off would not normally stop a system boiler.  You would of course get no hot water out of the tap.  Did the electricity go off?  did you turn anything off?

I agree, but No, we didn’t do anything. 

[ProDave]

17 minutes ago, Adsibob said:

I agree, but No, we didn’t do anything. 

My suspicion is the boiler just stopped and the malfunction has nothing to do with the water turned off.  If contacting plumbers just say it has stopped don't confuse the issue.

[Radian]

Vaillant eco tec plus 837 continuously 'loading'... 

Quote

+2 for pcb, don’t think I’ve known it to be anything else.

 

I seriously Doubt that.

[Radian]

1 minute ago, ProDave said:

My suspicion is the boiler just stopped and the malfunction has nothing to do with the water turned off. 

 

Maybe but what a coincidence! Just can't think of anything relating to water supply loss that could cause any kind of problem with a system boiler.

[Radian]

58 minutes ago, Adsibob said:

When we switch it on, the blue LED screen just flashes with the word "loading" coming up on the screen

 

Had you switched it off when the water went off? I mean - was it working, you switched it off, then the next time you switched it back on it wouldn't start up?

[Adsibob]

9 minutes ago, Radian said:

 

Had you switched it off when the water went off? I mean - was it working, you switched it off, then the next time you switched it back on it wouldn't start up?

No, we didn’t switch it off. We didn’t think to switch it off as the water went off without warning.

[Radian]

So what was on the display when you first noticed it wasn't working? Was it showing the "Loading" message?

[Adsibob]

6 minutes ago, Radian said:

So what was on the display when you first noticed it wasn't working? Was it showing the "Loading" message?

Not sure. I wasn’t in, the landlord popped in to take a look at it. He said he couldn’t fix it. I guess we will just freeze until Monday now. The flat is part of an 1890s block. Never been upgraded insulation or glazing wise.

[Radian]

Feel for you. Always happens on a weekend.?

 

From what I've seen online tonight and from experience it's probably the switch-mode supply on the main PCB. These are often the weakest part - specifically the large 400VDC reservoir capacitor which often have a rated lifetime of as little as 2000 Hours. In practice this is a de-rating that continues over its lifetime so some margin is designed in to keep the thing going over its warranty period. But past that, the power supply becomes too erratic and odd faults like this crop up. The controller isn't even managing to boot the firmware that would identify and display a fault code.

 

I've re-capped a few of these kinds of controllers before and there's a healthy market in refurbished ones like this as the fix can be done for as little as a couple of quid.

[CotswoldDoItUpper]

We had something similar with a similar boiler and it was something like the pressure switch. Simple £25 part from a decent plumbers merchant and a diy (with YouTube!) fix in about 15mins. We had an error code of f.75 I think. Hope it’s a simple fix for you!

[Adsibob]

Thanks all. Apparently Vaillant have an approved engineer call out service on a Sunday, so we will hopefully have it fixed tomorrow. 

 

[epsilonGreedy]

5 hours ago, Adsibob said:

No, we didn’t switch it off. We didn’t think to switch it off as the water went off without warning.

 

My boiler needs to be powered cycled off and on at its mains 240v connection if an LPG bottle runs out of gas before it will fire up again with a fresh LPG bottle.

[Temp]

17 hours ago, Radian said:

 

Maybe but what a coincidence! Just can't think of anything relating to water supply loss that could cause any kind of problem with a system boiler.

 

Bit tenuous but it's the only thing I can think of.... Suppose there was some corrosion causing a weak spot between the pressurised side and the mains. Loss of main caused the pressure difference across the weak area to reverse causing failure. When mains restored pressure is then too high.

 

But this would show up on pressure gauge or error code if boiler has over pressure switch.

[Pocster]

Diverter valve or solenoid for sure ?

[Radian]

2 hours ago, Temp said:

But this would show up on pressure gauge or error code if boiler has over pressure switch.

 

The boiler microcontroller appears to be fubar. Not getting past its boot-up and into the state where it can even report its own demise. Wondering if perhaps Thames Water also temporarily cut the local electricity supply either deliberately or accidentally. Power being applied to an SMPS is often the point at which it fails.

[Adsibob]

It’s a mystery, but it’s also a Vaillant boiler outside its warranty period, so no real surprises given I’ve never had a Vaillant boiler that didn’t start developing issues shortly after the warranty expired. Glad the new place has a Veissman!

 Couldn’t get an engineer out today, but we do have an appointment tomorrow. Hopefully being a Vaillant branded engineer, he/she will carry spares of whatever is needed.

It is very cold tonight!

Edited January 16, 2022 by Adsibob

[Adsibob]

14.5C in ours this morning. I actually thought it would get much colder with no heating.

[Happy Valley]

Surely the landlord that you mention should be sorting this out and ASAP as has a statutory obligation to provide space heating and hot water.

 

A good landlord will provide a few plug in oil radiators temporarily. 

Edited January 17, 2022 by Happy Valley

[Adsibob]

Boiler has now been fixed. PCB and gas diverter valve both needed replacing. We had an immersion heater so we didn't lose hot water.

Landlord is actually a close relative, so I can't really get annoyed with them!

I guess it was just coincidence that this coincided with the water being shut off. 

[Adsibob]

And it’s broken again. With a new PCB, we can at least see what error it is reporting. It seems to be so excited to have recovered that functionality that it’s reporting two:

 

 

 

time to call out the engineer again! What fun it is having a Vaillant.

 

 

[Pocster]

23 minutes ago, Adsibob said:

And it’s broken again. With a new PCB, we can at least see what error it is reporting. It seems to be so excited to have recovered that functionality that it’s reporting two:

 

 

 

time to call out the engineer again! What fun it is having a Vaillant.

 

 

As you say , at least you have errors reported …. A temperamental boiler reporting no error codes is worse . Valiant engineers in my experience of using them for decades are usually pretty good .

[Radian]

Probably just needs air bleeding. Must have been drained down to replace divertor valve. Some naughty air still hiding in primary somewhere.

[MJNewton]

A Google search suggests that first error might be a loose/disconnected flow temperature sensor. Perhaps that itself might then also cause the second error?