Vaillant Combi Compact heating won't shut off!

[nickthesafe]

VCW GB 242 EH The problem started last night, the heating came on (mode selected is summer hot water only), tried a few things and it went off. Missus phones me today - it's on again and with the temp dial at 1 the rads are steaming hot!. told her to shut off the main switch.. Got home this afternoon to give it a poke and a prod and can't find anything obvious as to why it would be doing this. So now we have to fire it up for hot water then switch it all off again. Your help and advice would be greatly appreciated, thanks

 

[Gasguru]

Faulty heating rocker switch?

I'm not sure whether a shorted hot water flow microswitch would cause your problem but worth a check. Big arrow below.

Untitled

• Gasguru
• 7 Aug 2008
• 1

 

[nickthesafe]

Thanks GasGuru - Yeah that was sticking (has done in the past), but this time seems something else has gone wrong - Can't get ignition anymore now she won't give us hot water at all, maybe it's time to admit defeat and get a new one???

 

[Gasguru]

Look up all the local boiler spares merchants and give them a ring. They may know someone that has good experience on older Vaillants. Although these boilers are old they're fairly bulletproof and well built. I've not condemed on yet...always been worth repairing.

 

[Agile]

If the DHW demand flow switch was sticking on it would think there is a demand for DHW and provide CH as the diverter is in the same position.

It sounds as if your poking of the system flow switch has stopped it from working any more.

These are totally repairable boilers for any competent boiler engineer.

Tony

 

[spacethegas]

the cam valve is playing up.
the connecting tubes etc will probably require cleaning.
perhaps powerflush.
as has been said before, no problem to fix.
you just need someone who knows what they are doing.

 

[nickthesafe]

The cam valve is acting correctly, everything seems to be mechanically 'right' when demanding CH or DHW, flue fan works, pump works, etc. but just no 'tick, tick, tick, whoomph'

 

[namsag]

have you checked over heat heat stat button doesnt need reseting.

 

[nickthesafe]

Thanks namsag, according to my book this button is located behind the LH side panel, but before taking it all off i couldn't see any wires go that way - there is however an identical looking device (black plastic with rubber buttton and a screw either side) behind and to the right of the pump, tried pushing this - no change, is there another one that needs attention?.

As a side note, I've been trying to get hold of someone before forking out upwards of £1500 for a new boiler, but so far no one has answered there phones or got back to me , anyone cover North Kent fancy fixing this if I have no luck???....

 

[namsag]

Yeah its usually in black rubber button. Try BG they do fixed price repair including parts for £165 ish

 

[spacethegas]

when you select c/h are both microswitches on the diverter activated ?

when you run the hot tap are both microswitches on the diverter deactivated ?

 

[nickthesafe]

Both switches?. There's only ever been one little red microswitch in the position shown...

 

[spacethegas]

remove the right hand side panel.
at the bottom towards the back is the diverter.
pull off the clear plastic cover.

 

[nickthesafe]

OK I'm an idiot - yeah, found it, Both the switches seem OK, here's how they are acting; Off - bottom switch in (spring loaded plunger) top switch out. CH both in. DHW both out. I've got BG coming Monday morning at £192 fixed price repair, no fix - no fee. if that fails i've got another contact well groomed on this breed. Truthfully I'm beginning to thing the control unit is stuffed as apart from the cam operated DHW switch this was the only thing i pulled apart after which it stopped working unless it DID overheat during the inital problem.... Thanks so far for you help, if anything that i've described defines an obvious fault please let me know so i can have a decent shower otherwise I'll wait and see what BG say and report the findings and or conclusion.

 

[spacethegas]

the cam moves all the way up & back down again when the tap is turned on & off ?[/u]