boiler not firing up please please help!

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clarelouise | 23:33 Fri 11th Jul 2008 | Home & Garden
11 Answers
Our boiler isn't firing up at all.
We have come home from hoiday and it was on for 2 hours then all of a sudden house went cold.
Pilot light is on but if I turn it up to number 1 from low it will fire and then go off after 2 minutes.
Radiators are stone cold.
My husband has put a new thermocouple on tonight and that hasn't done anything at all.
It won't fire up at all now.Just pilot light on.
It is a BAXI WM 512 RS.
It was fine when we went on holiday and 2 hours afer we got home.
What could be the problem.
Can anyone shed any light on the matter.
We are rather cold.
Our daughter has started with an infection and she has Cystic Fibrosis and we really need to keep her warm.
Please if ther are any plumbers out there or anyone with knowledge of this matter please would you reply and help us out.
Many thanks in advance.
It is much appreciated.


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Sounds to me very much like the pump might have gone!
Shouldnt be too expensive to have replaced, you might even be able to free the pump by removing the centre cap from it and depending on the type either use a screwdriver or a pair of grips and with all power off manually turn the rotor a few times. ****** BEWARE****** you may get some water coming out if you remove the cap but 9 times out 10 it is containable!!
if this doesnt work I would be calling a plumber, or British Gas should come on saturday and fix it for a set price of around �140.

Hope this helps, good luck
Question Author
Thank you so much for your reply.
Much appreciated.
I'll get my husband to take a look.
Most grateful.
I AM NOT A PLUMBER but when this happens to me I usually solve it with fitting a new therma-couple.

the thermocouple controls the pilot light, if the pilot light is on then you do not need a new thermocouple.

could be the following

1 - the gas valve needs replacing.
2 - the pump as already mentioned, if the waters not circulating through the boiler it will overheat and cut out.
3 - the thermostat may need replacing, try turning the thermostat up to full, 1 is very low and if the ambiet room temp is quite high then the boilers not going to fire for long.
4 - faulty room stat if you have one.
5 - cant rememeber off hand what features your boiler has but could be the transformer that lifts the gas valve.

you really need to call someone in urgently, cannot diagnose accurately over the internet and you cannot repair it yourself anyway.

if your in the birmingham or surrounding area let me know.
Question Author
Hi there,
My husband hasn't had a chance to look yet.
He has just arrived home form work.
He's going to look.
I tried the hot water this afternoon as I'd set the heating to come on this morning but it didn't come on.
So I turned it off.
Just decided at lunchtime to try the hot tap and the water is hot.Still no heating though.
Does this shed a little more light on the matter?
Thanks for your reply.
We are in Sheffield.
diverter valve is stuck, i think they give priority to the water and then the syncron motor switches the valve to the mid (heating and water) position or to the heating only position to give heating when its demanded, very common problem, will need either a new syncron motor or possibly a new head or in a worst case scenario a complete new valve and head.
turn the water off and heating on at your programmer, make sure your room stat is turned up high if you have one and if your husband finds the valve, which is normally near to the hot water cylinder and pump, they have a little lever on the side, if he uses his finger to manually move the lever over and the boiler then fires up then yes the valve is stuck. you can lock the lever in the heating position to give some temporary heat by wedging a screw in the gap between the lever and case to stop the lever springing back to the water only position. i'm not brilliant on the old style systems as ive been brought up on combis and i know that theres one way my father temporary locks the valve so you can get heating as long as you have the water on too, trouble is when the water reaches temperature the heating goes off too.
to help identify the valve they are commonly made by honeywell or danfoss and have a silver metal case or a white plastic one, they are about 6 inches long and rectangular. be warned that the valve is 240 v so caution is needed.
i reccomend you call out a heating engineer asap as your husband is going to need knowledge of plumbing and electrics to change or repair the valve.
i think gasman who uses this site lives up your way somewhere but i'm not sure how far he is from sheffield.
Question Author
Hi thanks so much.
My husband is going to have a look.
You have been very helpful.

just been thinking about your problem, the boiler firing up when you turn the thermostat up does not tally with the diverter valve being stuck, but if you've got how water but no heating its usually the diverter valve. you haven't got an electic immersion heater thats been left on and giving you hot water have you?
what was the problem with your heating system in the end?
Check your electricity supply (e.g. check fuses on consumer unit and lights in room where the boiler is located).
Check the gas supply (e.g. by lighting your gas cooker and/or gas fire)
Check the pressure on your boiler (it should be between 1 and 1.5)
Reset your boiler (press the reset button - check instructions for details)
Leave your boiler switched off for at least give minutes. Then turn back on.

I found more information here:
<a href="
not firing up</a>
I had similar problem with a Baxi Solo, but the pilot light was not on, instead the fan light was on and Boiler-on was on. The problem was with the pressure macro switch. The macro switch has to switch for the boiler to fire.

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