pilot light goes out after gas control knob is turned

[mcgilion]

Hi all

I have an old boiler - a Corvec Maxiflame II (http://www.chaffoteaux.co.uk/uploads/img42aee71f914061.pdf).

Its probably about 28 years old. But as they say - if it aint broke dont fix it. However now it has broken, so.....

Symptoms
===========
The pilot light can be lit ok by turning the gas control knob on the front of the boiler to the "ignite" position and pressing the electric ignition button. The light stays on indefinitely when the gas control knob remains in the ignite position (no problem there) but to light the main burners the gas control knob must be turned further to the full extent of its rotation.

However as soon as the control knob is turned away from the ignition position the pilot light goes out. I have tried this many times and am always getting the same response.

Background
=========
A couple of years ago a gas engineer swapped what looks like a thermocouple for me because of a similar (identical) problem. The thermocouple that he swapped out had some charring on the hot sensor (I still have this thermocouple so I can still see this now). From memory the symptoms are the same this time round so I am guessing that there might be the same problem again - the thermocouple is charring and perhaps the current differential is not enough to trigger the electromagnet to keep the pilot lit and open the valve for the main burner. If this is true then the underlying problem has reoccured. Perhaps its a thermostat cutting in and killing the flame.

Solutions
=======
Any ideas? Change the thermocouple again (its not even 2 years since this was last done)? Change the burner that lights the pilot and charrs it? Change the bolier and be done with it?

Thanks
McGillion

 

[GforceJames]

Thermocouples seem to be like lightbulbs, some last for ever, some don't. The factory fitted originals last the longest to ensure no warranty issues, i personally change thermocouples at every service unless its still the factory original.

James

 

[mcgilion]

any other ideas? help!

 

[Gasguru]

Plenty of other reasons but since several involve the gas parts suggest you get someone in. Its so old many may refuse to touch it though, probably time it was junked.

Of course you have been saving up for a new one haven't you.

 

[namsag]

If pilot i burning correctly and it is not the thermocouple, the part that the thermocouple connects to is duff whole valve req and cost around £200 just for the part. If you can get it for a model of that age

 

[Ric Me]

I have the exact same boiler and the exact same problem.

Mine started after I drained the system. I drained everything (to flush and retreat) and after filling I now get this problem.

I would love to know what solution you had in the end?

 

[namsag]

OOPS . Just re read what boilerit is... There is a fusible link attached to the thermocouples on these boilers its fitted at the top of heat exchanger and acts a overheat protection . basically it is like a bit of solder that melts if boiler gets too hot.

on empty these you have to make sure all air is out of system and only let it fire for a short spell at a time so link does not melt before all air is expelled and ytem can run normally

Part number is 33509