Vaillant combi boiler VCW GB 242 EH

[Clive R]

I am having problems with my vaillant combi boiler. All appears to be working fine but the burner will not light. This does not always happen, sometimes it works fine.
I have narrowed it down to the ignition transformer as the rest of the boiler seems to be working (pump, flue fan etc..)
Can anyone confirm this? Thanks.

 

[micky p]

I am having problems with my vaillant combi boiler. All appears to be working fine but the burner will not light. This does not always happen, sometimes it works fine.
I have narrowed it down to the ignition transformer as the rest of the boiler seems to be working (pump, flue fan etc..)
Can anyone confirm this? Thanks.

worth checking the differencial valve opens. Black plastic valve facing you when you take front cover off.
Also make sure there is no air in the system as they will not light up until it is fully purged.

 

[pannierstan]

Older Vaillants are some of the most over engineered boilers on the planet so be careful before you jump in. Any chance you can get hold of someone who knows how to work on them?

If it was the ign tranny then you would be expecting a lockout situation which you dont mention or isnt happening.

If the boiler simply isnt lighting at all then it is because it hasnt reached that point of the ign sequence.

Are you sure pump AND fan are running as the Divertor valve can cause problems on these boilers. Also agree with Micky re Differantial valve.

You might be really unlucky and have a duff vacuum pump on the gas side. This pump should pull at least 10mb (I think) when tested. Its sited on the back of the control box. Also the tubes and connections can sometimes fracture!

Stan

 

[Clive R]

Thanks for the advice. It's difficult as the boiler works well one minute, then not the next? Thanks again, will check parts tonight.

 

[DP]

pannierstan, good post. One disagreement though. Vacuum pump is an air pump. Also when it fails, boiler stays on low gas rate.

I would be looking at the diverter movement to see if the 'end of travel' mocroswitches operate and then take it from there.

 

[pannierstan]

pannierstan, good post. One disagreement though. Vacuum pump is an air pump. Also when it fails, boiler stays on low gas rate.

I would be looking at the diverter movement to see if the 'end of travel' mocroswitches operate and then take it from there.

Reading my post it does sound silly to suggest a vacuum pump would provide + pressure. Apologies. For some reason I have always called them that, but quiet incorrectly of course. Thanks DP

Stan

 

[Agile]

Can either of you explain why the air pump is needed?

I have concluded that its a design bodge because there was insufficient pressure available from a venturi to operate the gas valve !

Tony

 

[micky p]

Can either of you explain why the air pump is needed?

I have concluded that its a design bodge because there was insufficient pressure available from a venturi to operate the gas valve !

Tony

I think it was vaillant's alternative to a DC operated modureg at the time and several have failed over a time.

 

[pannierstan]

Can either of you explain why the air pump is needed?

I have concluded that its a design bodge because there was insufficient pressure available from a venturi to operate the gas valve !

Tony

As Micky said Tony its a totally over engineered way of regulating gas supply like a solenoid, but your explanation may well be right.

Stan