Hot water OK, heating not working

I've got a 10 year old central heating system (Potterton Prima boiler, Grundfos Super Selectric UPS15-60 pump - all has been fine up until today.

The hot water system is heating up fine but the central heating system is not getting hot. The boiler will run for a little while after cutting out by turning up the thermostat but I suspect it's just heating the hot water even hotter and the heating system isn't taking anything, I've tried bleeding it - all seems fine. Central heating pump failure? How can I check? Any advice appreciated.

We had same problem with Potterton Profile. The pump and valve had to be replaced which is fairly straightforward as we did it ourselves. This cured the problem but we were told not to use the boiler until work had been done.

Is it a fully pumped system. Have you a thermostat to control the hot water on the immersion tank?

You can usually feel if the pump is working vibration etc.

Happy days

Thanks for the advice, I replaced the pump....no difference, then did some root cause - despite switching currents coming through to the valve motor, the valve wasn't moving and moving it manually only provided brief (~ 2 secs) of heat, replaced just the valve head and hey presto all is well.