Vaillant VCW - Please can anyone assist?

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14 Sep 2018
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HI all.

I have a Vaillant VCW ( I think) it is probably 30 years old or so. Hot water works fine. I changed it to a digital thermostat about 2-3 years ago, but recently it seems there is some kind of "inbuilt" thermostat on the Boiler. In short, i've had two separate engineers come who couldn't get the heating to come on and said it can't be repaired. I was about to fork out £4k on a new boiler, and all of a sudden it suddenly came on and worked fine until it got warmer and then it seems to stop working again.

Is there any reason why the heating is not coming on in summer/spring months? There doesn't appear to be any buttons i can see.

An engineer tried to disable my digital thermostat and a direct connection and the heating still wouldn't come on.

Any advice appreciated! It's getting a bit chilly now so would like it sorted asap. As a bonus my heating costs have surely gone down!

Just to add, hot water works without fault and it is fully filled with water etc.

Pic below:
https://imgur.com/a/Try4v0k

Thanks
 
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asuming the external controls are ok the issues with this boiler are a problem with the built in time delay or the boiler not moving to hearing position on the valve making the micro switch ,the second fault is very easy to see ,get a engineer used to older boilers
 
When I put heat on (as in turn my thermostat higher than what the temperature is showing) nothing happens, it doesn't ignite etc. But as i say when I put hot water on it fires up immediately with no issues!

any ideas on what the issue is? As I say, it will most likely start later this month or early October!
 
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What can you expect Ian and bunnyman. When boiler installers see this beastie, they do not even know how the panels come off let alone how the boiler works
 
A control problem as in the thermostat? Or something else inside the boiler?
 
could be either but first thing is to rule out all external controls by disconnecting them at the boiler and putting a link in
 

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