can anyone help...a new thermocouple and cap have recently been replaced in the apollo 65/50b boiler we have. Prior to this replacement the main burner was taking some time to fire up when turned to continuous. Since the replacement the pilot light remains lit but the main boiler will not ignite even when the thermostat is set to high. Having being ripped off previously some knowledge of what the gas safe engineer will need to do would be appreciated. Many thanks

E. Bolton, March 2010

When the sensor gets hot enough from the pilot flame the control board opens the main gas valve.

You may have a weak pilot flame from a partially blocked injector - a defective sensor - a defective control board - a defective gas valve. You should be able, if you have a multimeter, to check for voltage being sent to the main gas valve. Any sensible sevice engineer would make this check first - it's quick, easy and costs nothing. He would then work backwards from there.

I an not quailified and have no experience - my advice is worthless.

Good luck...

Peccavi, March 2010