VAILLANT BOILER PROBLEM

[ellisjean]

Hello
Can any one help with this.
We have a Vaillant combi boiler, its about 20 yrs old, ref VCW GB 242 EH.
The boiler is working fine for the domestic hot water, but it will not fire up for the central heating! The pressure is when cold is always at 1bar.
Thank you

 

[twgas]

the water section on these are prone to sticking, now they are getting on a bit, that might be your problem.

 

[bengasman]

Is that a combi compact?
Probably nothing that a good clean won't sort out; they don't like dirty systems.

 

[bellairaphon]

do u have a roomstat, timeclock?

 

[Beerlover]

This may be a very simple repair that you can do yourself....

Remove the grey panel, in the centre of the boiler you will see a valve with four copper tubes coming out of it - this is the servo valve. It is held in place by one screw bottom left. Remove the screw, ove the valve to the right and forwards - gently. Feal behind for a silver pin from the water valve. Lift this up and out. thoroghly clean and regrease this. (you might want to turn the adjustment screw in one half turn) Reassemble and try the heating again.

If this does not fix the problem, there may be either a blockage in one of the tubes, the water valve may be shot, or very unlikely the diverter valve may have gone. There are repair kits for these but you will have to decide if you are upto this or you need a RGI to carry out repairs to these

 

[ellisjean]

Is that a combi compact?
Probably nothing that a good clean won't sort out; they don't like dirty systems.

Many thanks , others have suggested giving it a clean

 

[ellisjean]

do u have a roomstat, timeclock?

Hi, yes room thermostat & time clock. the clock is set to 'constant' and I have turn the thermostat right up to try and get the thing to fire!!

 

[ellisjean]

This may be a very simple repair that you can do yourself....

Remove the grey panel, in the centre of the boiler you will see a valve with four copper tubes coming out of it - this is the servo valve. It is held in place by one screw bottom left. Remove the screw, ove the valve to the right and forwards - gently. Feal behind for a silver pin from the water valve. Lift this up and out. thoroghly clean and regrease this. (you might want to turn the adjustment screw in one half turn) Reassemble and try the heating again.

If this does not fix the problem, there may be either a blockage in one of the tubes, the water valve may be shot, or very unlikely the diverter valve may have gone. There are repair kits for these but you will have to decide if you are upto this or you need a RGI to carry out repairs to these

many thanks, it is just as you described, so I will try giving it a go and get back to you!

 

[ellisjean]

This may be a very simple repair that you can do yourself....

Remove the grey panel, in the centre of the boiler you will see a valve with four copper tubes coming out of it - this is the servo valve. It is held in place by one screw bottom left. Remove the screw, ove the valve to the right and forwards - gently. Feal behind for a silver pin from the water valve. Lift this up and out. thoroghly clean and regrease this. (you might want to turn the adjustment screw in one half turn) Reassemble and try the heating again.

If this does not fix the problem, there may be either a blockage in one of the tubes, the water valve may be shot, or very unlikely the diverter valve may have gone. There are repair kits for these but you will have to decide if you are upto this or you need a RGI to carry out repairs to these

Hi Beerlover
The water valve is working for the hot water, the pin comes up and activates the micro switch, so I assume this isnt shot!
When the room thermostat call for heat the pump fires up on the boiler but nothing eles! What does the diverter valve do? How would I know if this is faulty?
Cheers

 

[Beerlover]

The servo valve has a rocker at the back that has to return to it's rest position to activate the diverter valve and allow heating to fire up.

If the pin is sticking it won't allow the servo valve to return to its rest position. Try pressing the right hand side of the black rocker and see if it fires. If it does follow the advice about cleaning and greasing the pin.

A sticking water valve will hold the pin up slightly and stop this.

The diverter valve is on the right hand side beneath the pump you should be able to see the valve move fully to the left for heating demand. Blocked tubes will stop this, also the microswitch may have gone, so the servo tubes and diverter valve could be ok, and the boiler is simply not getting a switch live.

Have a fiddle and look and let me know

 

[ellisjean]

The servo valve has a rocker at the back that has to return to it's rest position to activate the diverter valve and allow heating to fire up.

If the pin is sticking it won't allow the servo valve to return to its rest position. Try pressing the right hand side of the black rocker and see if it fires. If it does follow the advice about cleaning and greasing the pin.

A sticking water valve will hold the pin up slightly and stop this.

The diverter valve is on the right hand side beneath the pump you should be able to see the valve move fully to the left for heating demand. Blocked tubes will stop this, also the microswitch may have gone, so the servo tubes and diverter valve could be ok, and the boiler is simply not getting a switch live.

Have a fiddle and look and let me know

Hi Beerlover
Many thanks again for the pointers. I will have a go and let you know
ellisjean

Hi Beerlover
eureka!! I pressed the right hand side of the rocker switch and the boiler fired up. So I will strip it down and give it a good clean over the weekend.
Many thanks for your help with this one, I will let you know how I get on.
Ellisjean