Vaillant Ecotec Plus 937

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Surrey
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Firstly apologies for the long post but a lot has happened!

I have a Vaillant Ecotec Plus 937 that was fitted in October 2008.
It has been serviced annually and there have not been any issues until Feb this year when the boiler started making a vibrating noise when the pump was on.

I have a service agreement with npower and called them out. The engineer diagnosed that the bearings had gone in the pump and ordered a replacement. This was fitted and it was then discovered that a 'connector' pipe was leaking (It's a copper pipe that looks like a stretched 'S'), this was also replaced and then replaced again when the initial one proved faulty (It was leaking due to a dent at one end).

Whilst awaiting the second connector pipe the boiler started to develop the dreaded F81/F91 fault. Through looking at this forum I knew that this could be reset so I did this. I spoke to the engineer on his next visit. He didn't know much about this and said to call npower back if it did it again.

Needless to say it has now been 3 months and npower are still trying to resolve this issue.

They have replaced the following parts in this order -
NTC sensor
Divertor Valve
PCB

and today the heat exchanger/plate was removed and cleaned - the engineer said it was a bit dirty but not the amount he would be expecting to cause this problem and two thermistors were replaced.

A couple of hours after the engineer left the fault occured again but whereas previously it has happened once or very rarely twice a day it happened three times in the space of an hour and even after I reset it there is still only a very small amount of hot water before it runs cold.

When this happens I get the tap symbol on the display but no flame symbol which makes me think that the storage tank is partially filling and that this is the hot water that I am getting out. The boiler appears to be failing to ignite the burner when I am drawing hot water.

When the small amount of hot water is exhausted the 'C' symbol flashes for ages to show that the storage tank is recharging? but I only get the flame symbol for a short while then code S20 is displayed.

The engineer said today that if cleaning the heat exchanger didn't fix the problem then it was probably the APC pump that needs replacing which is the pump that feeds the storage tanks?

I managed to get hold of a diagnostic flow chart from Vaillant via email which the engineer has worked through previously to eliminate any non-part related issues and last time he was here before today he spent some time on the phone with Vaillant technical who suggested cleaning the exchanger and/or replacing the APC pump.

My questions are -

Has anyone else experienced this and how was it resolved (All of the engineers that have previously visited have stated that they haven't worked on a 937 before so a bit of experience might be of benefit)

Why would the DHW not be triggering the burner. Could this be linked to the fault codes or is this something else? No fault codes are displayed when the burner fails to ignite.

And lastly (not sure I want to know the answer to this but) this has been going on for a while, what is npowers policy with issues that they can't resolve? I'm obviously being a bit pessimistic because this has been going on for so long now and there doesn't seem to be an end in sight.

If you've made it to the end without falling asleep you have my thanks!
Any advice / previous experience would be welcome.
 
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I would suggest getting a Vaillant technician in.

I have found that the 'also rans' don't really understand the Vaillant system and controls and aren't that interested either! :cry:
 
You are best to deal with this as a complaint to Npower.

Most of these schemes have an arrangement to call a manufacturer's engineer when they cannot fix a fault.

Tony
 
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Tipper & Agile - That's what I was thinking if npower couldn't sort it but I didn't know that npower may arrange that. I'll dig out the T&Cs to see if it mentions this anywhere.

Mick - They have already changed a PCB. Is there a separate one for the storage tanks? The APC pump is next which I understand is the Storage tank pump?
Do you have experience of this type of fault?

Update - Last night the hot water started to work again so that now when I turn on the hot tap the burner ignites and I get constant hot water.
 
Mick - They have already changed a PCB. Is there a separate one for the storage tanks? The APC pump is next which I understand is the Storage tank pump?
Do you have experience of this type of fault?

yes seperate pcb top right at the back. It was modified to help combat this fault
and yes I used to work for vaillant.
 
Tipper & Agile - That's what I was thinking if npower couldn't sort it but I didn't know that npower may arrange that. I'll dig out the T&Cs to see if it mentions this anywhere.

How they arrange to get the repairs done is up to them and not expected to be featured in their T&Cs

But you need to create a complaint if they are unable to repair it within a reasonable time scale.

Tony
 
yes seperate pcb top right at the back. It was modified to help combat this fault
and yes I used to work for vaillant.

In that case they have replaced the incorrect PCB. The one they have already changed is on the front behind the electronic display and I'm pretty sure that they changed this thinking it was the one with the software glitch that has been discussed in other threads.
 
Changing PCBs is often done by engineers who dont really know what is wrong with a boiler!

Tony
 
hi, have you got a VR61 connected to that boiler?

i had a simillar issue a few months ago where when you run the hotwater, the tap symbol would appear on the boiler but it would not ignite. Switching off the VR61 and restarting the boiler cleared the fault. i had to replace the VR61 which cured the problem.
 
Joe,

Forgive my ignorance but I'm assuming a VR61 is a separate component to the boiler and not inside it?? If so I don't have one. The only Vaillant product I have is the boiler.

Thanks
 
hi, the VR61 would be a separate box if you had underfloor heating or separate zones.

what controller are you using?
 
Nope definitely don't have a VR61 then.

The controller/thermostat is a Salus
 
they probably already know the store pump needs changing but just bumping it along as its a pig of a job. not uncommon practice for these insurance companies. I can do it in an hour or so but I have done dozens, i would imagine first time they will need a few hours. Also will require very good access from the bottom.
 

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