vaillant boiler problem

My vaillant boiler which is 15 years old is giving me a bit of
trouble. Firstly the pilot light won't stay lit. It ignites up when press the button and ignite it but as soon as i relase the button i goes out. Secondly the central heating isn't working. when i put th thermostat on the water pushes out release valve and the switch i activated but the flames in the bolier doesn't increase. Not only tha it seems like the pump isn't pumping. Also the pump is really hot. an ideas what could be wrong and what kind of price to fix this
-- bbuk
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Sounds like a lot of problems. You can take a little disc with a slot in it off the front of the pump and see if you can turn the shaft, which should be visible. At least that'll tell you if you have a siezed pump,
Andy.
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On Mon, 17 Oct 2005 17:35:12 +0100, bbuk wrote:

Sound like there are a number of problems. It might be something like a VCW 242 or VCW 221 with permanent pilot. The first problem is (almost certainly) the thermocouple about 15 quid (This has connections for the O/H stat in series before people start telling me what a 'universal' t/couple costs from Wickes). Fitting about 15minutes tops.
The other symptoms might be a stuck/failed pump which would then cause the boiler to boil and throw out steam/water via the blow off pipe to outside. In fact the first problem might be that you can't relight until it's all cooled down? Does it sound like it's tumble drying rocks when this happens, with the pressure gauge going beserk?
Whilst there are many Vaillant boilers which are more than 15 years old and still going well it might just be time to call it a day but if it's not otherwise leaking a new pump and maybe t/couple might fix all the problems.
My guess if you were round here would be 50 to look at it and likely around 200 to fix if it's the pump and t/couple only. If the estimate was over 400 to fix all faults then new boiler time.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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The pump is fine because i took the screw out and switched it on and i
seems to be spinning fine. The pilot is working now but the centra heating still doesn't come on. is there anything else i could check would a faulty thermostat stop it from working
-- bbuk
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On Sat, 22 Oct 2005 17:21:00 +0100, bbuk wrote:

OK. Model number? You now have a boiler which works for HW and does not trip the O/H stat?
In that case it must be the diverter valve or maybe the servo valve
The diverter is a large component on the lower/back/right part with a number of 4mm tubes connected to it. The servo valve is a triangular black plastic gizmo on the lower/front/middle.
Changing either of these components is fairly involve even with the manual in front of you.
--
Ed Sirett - Property maintainer and registered gas fitter.
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i'm in Northants. If any of you guys could have a look or repair it i'l
pay you. I rang about ten people and they say they'll come on a certai day but never turn up. I can't seem to find the model number. I'll ge some photo's of the boiler and post it up. I can get the centra heating going for a about 15 seconds if i push the spring loade mechaanism in the centre which u have described. after that it cut out
-- bbuk
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done a bit more testing. when i turn the hot water tap on water pressur
pushes the spring loaded valve open and then hits the switch whic increases the flame on the burner. also a valve pushes outwards on th side and releases two switches. When i put the central heating on th spring loaded valve doesn't open. the valve on the side pushes out. T me it seems like water pressure isn't opening spring loaded valve lik the hot water does. if push the spring loaded valve by hand it sets th burner alight and after 20 seconds it will go out. the temperature rise to 60 some times. what do u reckon guys? the boiler was fitted in 198 if that help
-- bbuk
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On Sun, 23 Oct 2005 16:22:26 +0100, bbuk wrote:

Sounds like you definitely have a 221 or 242.
This is how it works.....
DHW flow operates on the diaphragm gizmo at the bottom middle front this pushes up the spring /cam arrangement make a micro switch whimh starts the pump.
The servo valve also on that cam thing now arranges that pump which has started will make the big diverter valve assembly move top the right (IIRC). More micro switches then initial the ignition sequence and you have DHW.
For CH the control having received the demand will start the pump, the spring/cam will have move back down and will stay down the servo valve will now arrange those 4mm pipes to push the diverter valve to the left (IIRC) and more micro switches start the ignition sequence.
1) Check that the DHW flow is correctly moving the spring/cam for DHW. 2) Check that the spring cam goes back and stay back after DHW and during CH. What you describe is not a fault.
3) I'm certain that on a correctly operating 221 or 242 the diverter valve rests in 'neutral' and then moves to the left (nigh on certain about that) for CH and the other way for DHW.
If you manually move the spring/cam then the boiler will think you are running a tap the boiler will try to heat the DHW but will cut out when everything gets too hot after about 20 seconds?
Without seeing it I would guess your problems are the following:
1) The spring/cam might be sticking in the DHW position or at least not fully returning to the CH position. Easy to check.
2) The diverter valve has gone. My money is on this one, one of the symptoms of this part failing can be that the valve moves in the same way for both heating and HW.
Frankly if this was a Haynes manual we'd have 4 or 5 spanners on this job. The price of the DV is not that big (less than 75 quid) but the procedure to exchange is a couple of hours work or so. The whole boiler has to be drained on primary and DHW sides. Other components have to be removed. The little servo lines are difficult to get out with out using excessive force and even easier to forget where they go back - they are all a little different to each other but not obviously so.
The diverter valve on these units is fairly reliable. Partly because using primary pump pressure the whole unit can be made very much 'heavier' than cheaper combis of that age. The diaphragm unit at the front only has to move that spring/cam/micro-switch/servo valve. Which IME is still the commonest non electrical fault on this boiler.
I beleive that Vaillant have a service division and they should be up to it. Try 0870 6060 777.
--
Ed Sirett - Property maintainer and registered gas fitter.
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