I have a potterton puma 100e. I tried to turn on the central heating but there's no heat reaching the radiatiors. There's plenty of hot water at the taps and the shower. When I turn on the CH the water seems to heat up past the diverter and goes about 1m down the pipe to just before the first junction. It's not very easy to get to. I checked the pump and it seems to turn fine when I unscrewed it a bit and pulled the spindle out a little. I'm guessing there might be a blockage in the pipe. I don't know if it would be air or sludge or the best way to go about getting things running again.