Vaillant VCWGB 242 EH Intermittant central heating

[TipTopPete]

Hi i am a fist time user of this site and apologize in advance for stupid comments or mistakes !
I have Vaillant vcw gb 242/282eh which was installed in 1992. It has been reasonably reliable up to now.
In the past I have had problems with no hot water which I traced to a blockage in the water section & also replaced the diaphragm as a matter of course. (not to difficult !)
Then the heat exchanger started to leak apparently common for this model. So fitted new modified type (dont need the wife in the kitchen asking hows it going when doing this job !)
Then the fan came loose from the fan motor (fixed)
The problem now is that when switching on the central heating it can take up to 30 seconds or so until the burner ignites & fires up (hot water all ok & fires up 5-10 secs) Sometimes doesn't fire up at all.
Also when radiators reach temp unit switches off for 5 mins then tries to restart mainly unsuccessfully.
Will sometimes restart if you switch off main red toggle switch & leave for 5 secs before switching back on.
Wondering if it might be a problem with the diverter valve not triggering the micro switches or could it be something to do with the flame supervision circuit board ?
Any advise would be much appreciated
(PS I live in a soft water area)

 

[Agile]

It makes me wonder why Vaillant have a reputation for reliability!

It just might be the system flow switch is slow to activate on CH. You should watch it when the boiler is started.

Its given a stupid name by the makers but its just above the pump!

Tony

 

[scatmanjohn]

I think Agile is thinking of another boiler

Its often a build up of dirt in the small tubes that connect into the servo valve (at the front above the water valve...black plastic thing).

Or even dirt in the servo itself...or occasionally the diverter.

The not coming back after reaching temperature fault can be a pcb fault (don't ask me which one)

Be aware that there are two versions of this boiler (hybrid/non hybrid) before buying any parts.

 

[TipTopPete]

Thanks for your advise guys I will have a look at the weekend for dirt in
my water system ! !

 

[bengasman]

Take screw from centre of pump and see how fast it spins when call for heat. If the pump is almost dead but not quite, it may not build up enough pressure to move the lever against the micro switch on the diverter. Turn how water on and see if it moves out. Turn water off and heating on and see if it moves the micro switch. If you are not sure, either push the micro switch with tool or adjust the lever with the screw.

 

[TipTopPete]

Thanks for your info bengasman
I have just removed the pump screw & switched on the heating,pump seems to be spinning like a good'n ,what have noticed though is if I get hold of the plastic casing for the diverter valve stuffing box & give a tap it nearly always fires up, it then gets up radiators up to temp before switching off, when it tries to restart on its own it runs the fan and everything but ignition. I then have to switch off the red toggle switch wait a few seconds switch back on sometimes it will start on its own and sometimes a give the stuffing box a tap.
Cheers. Pete