Valliant mag 125/7 boiler will not light!!

[Nsr500rossi]

Hi trying to get the boiler working in my camper van, seems to be a very simple boiler, but i still can not get it to fire up ... I have the pilot light working and have changed the diaphragm and top housing so it is now leak free. But the boiler will not fire .. I have the water pressure working i have tried removing the water section and manually operated the rod that opens the gas whilst the pilot light is on, but still there is no gas coming from the main jets (if thats what it is called) Any ideas, i am a bit stuck many thanks Mike ​ ​

 

[Deleted member 25704]

Its a blocked pilot injector. Remove the pilot tube and the injector will reveal itself. Remove the injector and boil for a couple of minutes in water, this helps to remove the concresions. Reasemble and bobs your uncle.

 

[Nsr500rossi]

Really that simple ..cool

So i am dismantling all the pilot bits to find the injector?

Just to confirm, i do have a pilot light, but the boiler does not fire ..this is the pilot injector causing the problem?

Will report back

Many thanks
Mike

 

[Deleted member 25704]

When the pilot injector is blocked, I should have said 'partially blocked'. This means that it operates normally when lit, or enough to energise the thermo-electric valve - however, when the there is a hot water demand, the gas valve opens and allows gas to the burner, at this point gas pressure drops at the pilot. Because of the partial blockage, the pilot flame diminishes, and the thermo-electric valve shuts down.

 

[Nsr500rossi]

Ok, so i have dismantled it, well what i think is it ..

I have a metatal mesh (filter thing) a metal tube with holes in, which the metal filter goes around and a brass small injector, i think.

brass injector has a white piece of plastic in it with a tiny hole in the centre, is this the piece i need to clean?

Also, as per your last explanation, my pilot light never changed when i was trying to get the boiler fired up, the flame stayed the same.

i can email you a photo of the bits i have dismantled if you like.

thanks again for your help, i would buy you a pint if i could ;_)

Mike

 

[Nsr500rossi]

Just to add ...i hear no gas from the main boiler when i turn the hot water on, i hear the pilot gas but no main gas.

injector is in boiling water now

Mike

 

[stevetheplumber]

its got to be diaphram related digging into memory theres a adjuster on the water section try that in and outyou should be able to lift the rod manually with the section bottom of are you sure its not the rod siezed

 

[Nsr500rossi]

its got to be diaphram related digging into memory theres a adjuster on the water section try that in and outyou should be able to lift the rod manually with the section bottom of are you sure its not the rod siezed

Hi Steve

Yes there is an adjuster on the bottom water section, the dial is for water temp, if i turn it (with the the water part dismantled) nothing happens) well i can see the rod attached to the dial rotating.

There is a rod that i can push in and out, feels like it is on a spring, is this supposed to go up and down as i adjust the hot water temp dial.

Should this push the diaphragm or diaphragm plunger up, in turn opening the gas valve above?

Thanks

Mike

 

[Deleted member 25704]

If its not the the injector and you have changed the diagphragm, as Steve said, it could be a siezed rod. This can be cleaned with a non-metalic cloth and lubed with silicone grease.

but, before you strip the water section down, just isolate and pull out the mains-in connection - just inside the water section there is a hexaganal brass nut, remove this by unsrewing. This is called the venturi, it has a small hole near the tapered end, make sure this is not blocked.

 

[Nsr500rossi]

If its not the the injector and you have changed the diagphragm, as Steve said, it could be a siezed rod. This can be cleaned with a non-metalic cloth and lubed with silicone grease.

but, before you strip the water section down, just isolate and pull out the mains-in connection - just inside the water section there is a hexaganal brass nut, remove this by unsrewing. This is called the venturi, it has a small hole near the tapered end, make sure this is not blocked.

The water section is already stripped down ..

I can not find the brass nut you are talking about, the water section comes in 2 parts, top and bottom, in the top section there is a brass nut, but this is the nut that the diaphragm push rod goes through, before going into the gas unit.

I can not see and brass nut on the bottom section, just 2 large black allen bolts and a plastic bit (cap on the bottom) also a big flat head screw on the bottom.

Mike

 

[Nsr500rossi]

There is a brass nut on the inlet from the heat exchanger on the bottom water section, it has a hole in the middle, it is not blocked, is that the one you mean clanger?

 

[Deleted member 25704]

Where the cold mains comes into the bottom water section, look inside, and the brass instert has hole anlong its length, to allow water to pass through it, but lower down its shaft it has another smaller hole in it. This hole can become blocked due to limescale, or it may de-zinc and block with zinc-salt in soft water areas. Its called the venturi - I suggest you do an online search for the instructions, with an exploded view. It will help you get it back together again. Make sure you check all your gas connections for tightness with leak-detection fluid.

 

[Nsr500rossi]

Ok i will look inside for the brass insert, the inlet for the mains has a big nut on it, i guess the insert is inside.

Just put everything back together , will check it in a min when i have filled the water tank up.

Also someone on a camper van forum said it could be the thermo coupler, are they correct??

Mike

 

[Nsr500rossi]

I have removed the water inlet, there is no brass insert inside!!

The only brass hex piece is on the water section from the heat exchanger, that has a hole on it, this is not blocked.

Couple of other people have said water pressure, but i seem to have good water pressure, no air locks or anything.

Going back to the water section with the heat dial attached, how does this work, when i turn the dial i see the connected rod turning, does this just open a valve inside the water section to let the hot water though?

There is a push rod attached the the bottom part of the water section, i can press this in and out, it spring loaded, what does this do, should it go up and down when i turn the hot water dial (it does not at the moment)

How is the main gas valve opened, is it the water pressure pushing the diaphragm up which in turn pushes the round disc with the plunger rod attached which goes up into the gas valve , opening the gas valve.

thanks

Mike

 

[Nsr500rossi]

Could it be a blocked gas jet /Venturi inside the main gas valve?

 

[Nsr500rossi]

Oh my, clearly i am pretty stupid...


I was not turning the dial back to the gas on position, so click, light, dial springs back and thats how i was leaving it, did not see the little gas flame on the dial (it was slightly out of view from the side i was looking from)


I now have lovely hot water ...


Thanks to all who help, i really appreciate it, at least i now have a better understanding of how the boiler works


Mike

 

[Deleted member 25704]

Well done Mike, Happy camping!