Vitodens 100-W Cycles But Won't Ingite, No Error Message

[Jake48]

My 2007 Viessmann Vitodens 100-W30 gas boiler cycles continuously but won't ignite. There is no error message. This is the first time I have had a problem with this unit in which there was no Fault Code (error message).

In past I had stuck flapper in 2010 but got F-5 fault.

In 2011 I had low pressure from bad feed reg valve but got Low pressure fault.

The pressure is fine this time.

Is it a stuck flapper again? Is so, why no error message?

Anyone know what might be wrong?

 

[Jackrae]

when was boiler last serviced

I believe some of the early 100 units had problems with their ignition transformers and electrodes

 

[Jake48]

I just spoke on the phone with Viessmann's Tech service and he thinks because it is continuously cycling and there is no error message, it is not the pressure switch or ignitor he says it is probably the internal gas valve.

Does this sound right?

 

[JohnD]

This is a UK site and the boilers here are not the same as in your country.

 

[Jake48]

Ok a new piece of data. When it cycles, it is actually heating up for a few seconds so that means it is actually igniting, but then it shuts down. The internal temperature rises from 75F to 85F then drops back down.

Any clue to what the problem is?

 

[Jackrae]

Pump not pumping so boiler stops firing on high temperature limit as a "normal" function so no fault code required ??

 

[Jake48]

No. Flow is going, but then tapped on gas supply valve and is now working but that gas supply valve is obviously about to go.

 

[Bunnyman]

Nope

 

[Agile]

Why not call your local repair man?

Tony