No heating?

My heating didn't come on this morning. The thermostat was on high, but the boiler wasn't doing its thing.

A bit later the boiler came on for a while then went off, and I discovered that the radiator nearest the boiler was nice and hot but the rest were cold.

I then went for a fiddle in the airing cupboard and there is a 3-way diverter thingy in there that sometimes makes a buzzing noise (which has been worrying me for a while. All three pipes that go into it were warm

I had a switch on the side with MAN or OPEN. It was set to MAN so I moved it to OPEN and could hear water flowing. All three pipes rapidly went cold and the boiler sparked into life. I moved it back to MAN and so far the boiler has continued to burn and all the radiators are warming up.

Any idea what was wrong, why it started working and whether I should be worrying about that 3-way diverter thingy.

BTW, my boiler is a Potterton Suprima 40, in case it is relevant.


Thanks in advance