Hi looking for some advice, my boiler decided over the weekend to stop burning, in short the pilot light goes out, set the thermostat to max and the boiler to constant heating and water, hold the igniter button in and the pilot light's up, hold the button in for 15 seconds and release burner keeps burning for about 20 seconds and then goes out and the igniter button pops back out, am i right in thinking this could be a problem with the thermo coupling