i have a potterton puma 100e,the central heating works fine but the hot water only works when thr central heating is on and is slow running as well,any ideas?

jay, July 2010

When you open a tap, without the CH on, does a red light on the modulator board come on? This is the pcb behind the front switch panel with the front cover off.
If no, replace HW flow switch.
If yes, is the heat going down the CH flow pipe?
If yes, the wax capsule on the diverter is gone and needs changing.

Carefree, July 2010