Vaiilant combi-heater VCW sine 18 T3Wf h stop working

[tonyvat]

Central heating switch doesn't work. Red boiler switch lit and on. Nothing happens when switched to instant water or immersion either. no boiler firing up, no hot water from taps. Running taps does not prompt boiler to fire up?

Is it the switch/circuit board or maybe something else?

 

[The831Bunny]

Turn off the pilot by pressing the red button hard. Follow the instructions on the inside of the door to relight pilot. If no instructions: press in green button very firmly and keep held in, twist ignition sparker knob repeatedly till pilot has lit, hold green button in for a further 20 seconds. Slowly release green button. The pilot should stay alight. If not, wait 3 minutes and restart procedure, holding in the green button for longer. The pilot mechanism can become jammed/misplaced so relighting the pilot will clear that problem.

If still no joy, reset the boiler overheat thermostat. This is located on the right hand side of the aluminium control box. Slide your right hand down between the pump and the control box. You should find a black rubber button about 6-7 inches from the front towards the rear/bottom of the box. Press this in firmly, it may click, if it does your boiler should function. If the answer is no, then you need to contact a Gas Safe registered engineer to check the pump/pcb/loom. This is a job for a specialist. Be sure to ask that they are familiar with this model.

If the boiler operates OK for a while, then the overheat thermostat trips again, you need to get the cause of that checked as above too.

Hope that helps

Bunny

 

[tonyvat]

Thanks The831Bunny.

I neglected to mention that the instant hot water when switched on failed to work although when switched to immersion the boiler fired up and central heating also worked. Occasionally the immersion failed to work when switched on and occasionally the central heating when switched to on. The red switch bulb lights up and the fuses on the PCB seem in working order. I suspected this may be a malfunction with the PCB and now that neither the instant hot water, immersion or the heating work wonder if the PCB has died? What do you think?

Someone suggested replacing the diagphram but if the boiler worked sometimes in immersion mode and central heating mode is it likely that there is a problem with the diagphram?

Any advice or suggestions would be welcome.

Thanks

 

[The831Bunny]

Facts Facts Facts!

Can only base diagnostics on facts!

From what you are now saying you have a diverter valve problem and/or a water section problem

I guess we can assume pilot is on as you are getting some heat. Press left hand rocker switch in at bottom, and centre and right hand rocker switches in at the top (2 of them), does the boiler fire? If so does it then turn off after about a minute. If no, then likely diverter valve wax capsule is defective. It may also heat up the radiators during this time and the boiler stays on longer than a minute. this is incorrect. If it is working correctly the boiler will stop firing and the radiators will remain cold. This is the DHW pre-heat mode.

We best confirm this before we move on

Cheers

Bunny[/u]

 

[Agile]

Can you explain what you mean by "immersion" mode?

Because of the age of these boilers, by now they often exhibit several faults.

Some of the parts are no longer officially available.

Tony

 

[tonyvat]

Agile-when I said immersion mode I meant with the switch switched to immersion instead of instant heat.

Bunny

The pilot light is on and stays on at all times.

1. First of all the switch positions fired up the boiler from the pilot light except the switch when switched to instant heat instead of immersion. I left this for a couple of months.

2. The heating timer still activated the heating if need be, the heating switches and the switch turned to the immersion position worked, firing up the boiler from the pilot light.

3. Once or twice the switch turned to the immersion position failed to fire up the boiler from the pilot light (instant heat switch position still not working). I managed to set the heating timer to overide ON, (it had been turned to OFF for summer) which fired up the boiler and also allowed me to draw hot water from the taps. The immersion switch later worked again!

4. Now no matter what configuration of positions you switch the switches too or if the timer is set to activate the boiler, nothing happens. The boiler does not fire up from the pilot light. The pilot light is on still and the boiler above it is warm, no doubt from the constant pilot light heat.

Cheers

Tony

 

[Agile]

Where do you get the idea that its called an "immersion" mode?

Tony

 

[tonyvat]

Agile

I assumed that if the rocker switch was switched away from the labelled instant heat option to the labelled immersion option then the boiler was in 'immersion mode' rather than 'instant heat mode'. That is of course if the boiler works when the switch is switched to the immersion mode!

Cheers

Tony

 

[Agile]

I have never seen any Sine 18 labelled that way and as a combi that would not normally have any meaning.

Is this a manufacturer's engraved panel or something stuck on it later?

The normal function is in the top pressed it gives the DHW preheat and in the bottom pressed it gives the normal DHW but without the preheat.

"Immersion" implies to me a hot water cylinder with an electric "immersion" heater element and my thoughts go to a system where someone might want the combi to be off when a cylinder is to be used.

Tony