Vaillant sine flaky pcb?

[ianniann]

I have a Vaillant VCW-Sine 18T3WFH which seems to still work OK for the most part. This weekend it decided it was going to run the CH continuously. The clock and stat won't turn it off, pin 4 is stuck at 240V. Temperature regulation is fine so I think the NTC is fine and the burners go off if I ground the connector. The main power switch turns it off. The CH switch doesn't turn it off but does turn off the light in the main switch (!).

So I think the PCB has gone wonky. Could be the switch panel but they actually seem to do something so I think its the board. Any thoughts?

--ian

 

[DP]

There is no guess work involved. It is a case of locate the fault and fix.

 

[kevplumb]

how do you bust a sine 18

hand grenade comes to mind

 

[ianniann]

I thought this was the end of the line? What could possibly be pulling pin 4 live even when the time clock is off? Even with the time clock disconnected? Should I be tracing the circuit board to see where that signal is coming from?

I should have mentioned that DHW is fine although not very convenient because I have to have the boiler switched off most of the time to stop the house melting.

--ian

 

[namsag]

Threw a full set off boards for one of these in the bin last week as its been at least 12 years since i have seen one that needed them, still got 3 flowswitches though .
Will get the kids to show me how ebay works

 

[ianniann]

Thanks. I'll check the micro-switches tomorrow and see if one is stuck.

--ian

 

[Agile]

I have been to a Sine 18 with a faulty switch or switch pCB.

It was a while ago and I dont remember what the symptom was.

Rather unusually, I think I replaced the whole switch PCB as I had an old one to hand.

Tony

 

[ianniann]

I'm feeling happier. The water section microswitch(es) was apparently stuck on. I tweaked them off and now the heating works on the time switch instead of all the time. I don't know yet whether the diaphragm is knackered or fingers crossed the switch position is not quite right.

--ian