my boiler fires up when i turn my hot water tap on but when i turn up the thermostat, it doesn't fire up and it just makes a humming noise, but i have plenty of hot water.

Baxi Genesis 80 G.C.No 47 077 01

moirablack, May 2008

I had this a number of times - it was the 3-way valve (part number 235838) sticking. I cleaned it and lubricated a few times which worked for a short period but eventually replaced it when it stuck every few days. Since replacing it,about 18 months ago, the fault has not occurred since.

Duncan Clarke, June 2008

knackered thermostat?

iain, May 2008