hi steve, the baxi combi 80e has a water diverter section on the left hand side as you are looking in boiler with casing off and panel lowered, it looks like a big lump of brass with pipes all over it and wires ! anyway these are prone to playing up and leaking, if you look at it there are 2 micro switches on it one is on the top and the other on the end looking at you, these are activated by pins that push out from the body of the unit and push them in however these fail and the pins jam and dont push the switches anymore, you can test this by leaving boiler on and with a screwdriver activate the microswitches one at a time one of them will make the boiler fire up and the heating come on, if this happens then you know you've found the fault and the water section (or hydraulic section as some people call it) will need to be replaced this is around a £100 from any parts supplier...hope this helps...mark
mark the gay boiler man, November 2008
