Vaillant vc gb 242e

[Zacman01]

Hi,

I'm looking for guidance with regards to the above boiler, please.

The boiler Vsillant vc gb 242e has recently stopped working in that the fan and pump would run but no flame would establish.

I've checked the diff press switch, pump and air pressure switch, all in good order good boiler water pres sure too..

So, I changed the flame sensor and electronic control pcb. No different. I then changed the fan pcb which fired the boiler as intended. However, I now have the situation where if the system switches hot water to heating or vica versa the flame extinguishes and wI'll nit re-light. This is also the case when it switches via the timer but the fan runs and so does the pump but the boiler will not fire until it is switched off and on by the boiler neon rocker switch. It will then run until either HW or CH are at temp then refuse to fire up on next demand. In all cases the pump and fan run as intended .

My thoughts are with the motherboard or another possible faulty flame sensor pcb. Has anyone any ideas or checks to perform? I have followed the Vaillant guide fault finding but tbh draws a blank. Your support most welcome

Cheers

Zac

Ps having called 4 local boiler techs none have turned up or cant get out to me yet are more than willing to fit a new boiler over the weekend. Amazing ..new boiler is in the pipeline this summer but need a fix for now. Its been a fanrastic boiler and has never let me down in 20 years til now. I Just want a few more months out of the old gitl

 

[ollski]

I haven't been to one in a while but check that the pump proving switch return to rest after a demand.

 

[Bunnyman]

Is it a vc or vcw? Ie is it a combi

 

[Zacman01]

Thanks for your replies...it's not a combi. Hot water cylinder. How obvious is the pump proving switch to find and ceck? Thank you.

 

[Zacman01]

All the mechanical properties appear to be functioning g correctly. The Pressure differential vslve operates as ut should. I've tested the sir pressure switch by blowing / sucking the tubes connected and will fire the boiler after a restart if operated like this. In my mind I have doubts over the motherboard and wanted to know whether the make up of this would impede the firing of the boiler should it be defective? I may just replace it and see., but hope you fine people nay koiw better.

 

[ollski]

Save your pennies from being dished out on a pcb and buy a decent multimeter then test your components methodically. Blowing the air pressure switch won't help the delicate diaphragm.