Hi, my boiler stopped working last night,i checked the boiler and the pressure had drop so i topped it and to 1bar and it fired up, But now it keeps boiling the water until the pressure release kicks in,its the same with the hot water, i search the forums and i think its the NTC Sensor, if you short the purple wire connected to it the flames die,i also tested it when it was hot and it was 4.57ohm, do you think it is this before i buy one also is there pressure vessel to repressurise. thanks Rob
Vaillant vcw 18 t3wf h
- Thread starter the57
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After removing the sensor and testing it seems ok, 2.4 ohm @room temp and drops when you hold it, has anyone got a fault finding manual for this Thanks Rob
I think the first reading must have had a bad connection,I've got it working now,its got a leak on the back on the red tanks can't get to it unless you take it off the wall,i drained all the water out and filled it back up and bled everything and i could hear air then water on the back ,then it worked like it should. 
it will problely go again in a few days,thinking about getting a new one now if its got to come off.
it will problely go again in a few days,thinking about getting a new one now if its got to come off.
the red tank is the expansion vessel.
you can put another vessel on the return pipe leading to the boiler and leave the one behind the boiler where it is.
don't chuck the boiler out just because of this - you have one of the best combi boilers ever made. your new one will not last half as long.
you can put another vessel on the return pipe leading to the boiler and leave the one behind the boiler where it is.
don't chuck the boiler out just because of this - you have one of the best combi boilers ever made. your new one will not last half as long.
To be quite frank ,yes a very good boiler in it's DAY. So was the Ford Sierra a great car in it's day, get my drift. Also if it is a balanced flue you can bet the flue seal has failed on it by now,,,,not good.
yes it the expansion vessel,looked it up it cost £120,the flue seal is like new,well its still working and it stopped driping, something must have block the hole 
going to save up for a new one before its to late.
going to save up for a new one before its to late.
just fit a generic expansion vessel - £20 from screwfix. plumb it into the return pipe near the boiler. job done. put money saved towards eventual replacement of boiler.
Sound like a good idea, what size should get? is there room to push the old one up to cap it off?
as long as the vessel on the boiler is not leaking, then leave it as it is. no need to disconnect.
the size of vessel to fit depends on the quantity of water in your radiator circuit. 12 litres should be enough for most domestic installations. the one in the boiler is somewhere around 8 to 10 litres.
the size of vessel to fit depends on the quantity of water in your radiator circuit. 12 litres should be enough for most domestic installations. the one in the boiler is somewhere around 8 to 10 litres.
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Have you repressurised the expansion vessel? They sometimes leak on the seam if they are flat. Repressurise to 1 bar using a foot pump (with boiler empty). When you refill you will hopefully find the leak has gone.
Bunny
Bunny
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