Boiler not firing up after refill...help please

[Dougie212]

Hi there..

So, after flushing my boiler system to release what appears to have been an airlock in some pipework for my new radiator...(previous threads), I have today gone and bought some Central heating cleaner. Added it via a radiator, filled the system up, bled the radiators and the pump via the big centre screw as previously advised, all up to pressure...turned the boiler on and it switches on, but doesn't ignite....... the pilot light is lit, all the usual lights are on but its not igniting. Tried the hot water, and again, its firing up but not igniting. I only know of the centre screw on the pump to drain air out, is there anywhere else? Many thanks in advance. Ive *hopefully* attached a pic of the dam boiler.........

 

[leakydave]

Did it overheat through lack of circulation? If so there may be a reset button that needs pressing to get the boiler running again.

 

[leakydave]

You could even up the pressure a bit to force any air to high spots

 

[Dougie212]

Hmm I don't know if there is a reset button.. It seems prehistoric to ones I see these days but it works really well, normally. It didn't run while it was empty, and with regards to pressure.... Im always nervous of upping it above that red line.. Do you think Id be ok to up it? Do you know if there is any other air venting I need to do on the boiler?

 

[Dougie212]

Seem to have a bit more detail..... when I turn the boiler on, albeit nor firing I can hear the water bubbling around, especially when I turn it off.... so Im assuming there is air in the boiler now.... I have tried the big screw on the pump.. Is there any where else to try?

 

[The831Bunny]

Seem to have a bit more detail..... when I turn the boiler on, albeit nor firing I can hear the water bubbling around, especially when I turn it off.... so Im assuming there is air in the boiler now.... I have tried the big screw on the pump.. Is there any where else to try?

Make sure the cap is loose on the Automatic Air Vent top right rear of the boiler (look over the top). Give the brass canister a knock, the float sometimes gets stuck. You'll hear the air hissing out.

 

[Dougie212]

The air vent cap is as stiff as a board.. granted it's pretty mucked up round the back but it's not pushing at all... will I be ok to put some penetrating oil on it first before I try and loosen it.

 

[The831Bunny]

I'd gently try some pliers on the cap. Most times though a weeping/crusty AAV needs to be replaced. Part No. 061707 if you need it.

 

[Dougie212]

Managed to get some pliers on it, it looked plastic.... but got it to spin and did have a small amount of air, then water. Just to confirm it's ontop of a small tank in the right hand side at the back of the boiler. Have just drained it all down again to get rid of cleaner so will refill and remember to try and bleed that and the pump too... if I leave the plastic thing undone it squirts water....

 

[Dougie212]

So, the problems just keep coming.. I've refilled the system, bled all the air... gone to turn the boiler on and nothing's happening. I'm guessing there is power getting to it as the led in the switch is on, but when I set the boiler to CH on nothing happens. I get a slight hum coming from the pump. Just wondering if there is anything to reset it..?? I've tried the how water and again, I hear a click but nothing turns on.

 

[The831Bunny]

Sounds like your pump has stuck. Use a small electrical screw driver to turn the end of the pump shaft after removing the large chrome plug you've been venting from. Some cleansers can lead to the pump sticking after use.

Once the pump is running vent the AAV and screw the cap down if it's dribbling. It needs replacing to work correctly. Swap the boiler between HW and Heating to push the air out ⅚ times.

Any other work needs to be carried out by a Gas Safe registered engineer who is confident in older Vaillant boilers in afraid.

 

[Dougie212]

Thankyou so much!! I shall go and try that now... Will there be an exodus of water when I remove the large chrome plug?

 

[Dougie212]

The831Bunny... you sir are a genius.... I span the pump shaft, and it began working but didn't ignite still... so, I turned the boiler off and heard the water bubbling again in the boiler..... so, (rightly or wrongly) with the boiler running I purged the air from the AAV and with a whoosh, a huge spit of air until a flow of water, closed it and the boiler ignited.... thankyou!! still have an issue with one of my radiators not flowing out of th TRV on the right hand side which results in it staying cool along the bottom, but for now, that can wait..... thankyou very very much

 

[The831Bunny]

Glad you got it sorted mate. The boiler's Diverter Valve is powered by the pumped water in the boiler, so any air or the pump not working will stop the boiler from firing.

 

[Dougie212]

That's brilliant.. don't suppose your an expert on TRV's too are you? So grateful for your help mate..!