Baxi Combi 80 Eco boiler - no central heating

[Ralphy3]

Boiler has been on hot water only for the summer, when switched over to heating and hot water, can't get any heating. Boiler lights, gets hot, and cuts out after 15 -20 seconds or so. Heat exchanger pipe to diverter valve is red hot. Heating outlet pipe out of the boiler to rads and return pipe is cold. System pressurised to 1 bar. System is bled, including auto bleeder and pump, pump is running, but not circulating to rads. If hot water tap is opened, boiler ignites, tap runs good and hot, and central heating starts slow circulation - outlet pipe below boiler gets hot, but rads are not getting hot, and heating return flow to boiler stays cold. If I turn off all rads except the nearest one to the boiler, then it will warm up after half and hour (just warm). If I then run the hot water tap as well, then the radiator gets warmer, quicker. I suspect the diverter valve. As Hot water working ok and no sign of dribble at the microswitch pin, I assume the hot water diaphragm is ok and nothing to do with this. I am told (Plumb Centre) that the central heating diaphragm is not serviced - have to buy a complete new diverter valve - more than £100. For me everything points to the central heating diverter valve. Any advice on how to check it or am I wrong - any other suggestions? Thanks!

 

[Billy Bob Bob]

TBH ralphy no one is answering because no one wants to give advice on this peticular boiler its a nightmare,your best bet is to go direct to baxi

 

[Ralphy3]

Thanks Gasman. I phoned Baxi who were less than helpful, especially when he insisted they only give advice to registered gas fitters which I am not (competent plumber but not a registered gas fitter!). Had to get stroppy for him to even talk to me - told him it was a water problem not gas problem. Tried to get the conversation onto a "customer" level, he was just surly and the best I got was it could be several things....but no positive suggestions....So gave up. Lesson: don't expect too much from Baxi "Technical hotline", unless its in warranty and you are a registered gas fitter!
So I stripped the diverter valve down, starting at the hot water end and found that although the hot water was working, the hot water diaphragm plastic disc spindle that goes into the central heating part of the diverter valve had siezed in the bush (Opposite end to the DHW microswitch spindle). So hot water water was enabled, but when tap was turned off off, the spring could not push it back onto the central heating valve to open the heating valve allowing heating to circulate, the boiler then got up to temperature and cut out. Just cleaned it up, fitted a new DHW diaphragm as a precaution and problem solved. Thanks for your help!