Boiler fails to start when cold?

It may well be a component or a connection that objects to the cold but works fine when warm - you might consider a technique I used to use on computers 30+ years ago....

A hair dryer played gently on the control circuit and wiring may give you a tip - also slowly wriggle the wires about a bit to see if you can make a bad connection suddenly come good.

Once the boiler is operating then a can of freezer spray (Maplins £8) on the circuitry may well bring the fault on if it's being caused by a particular component.

I am not a boiler engineer.

Good luck...

Peccavi
February 2013