how can i fix my potterton 80e?

we can only give advice if you give us a sequence of what happens when you try dhw demand and then ch demand for example.
we're not magical, we diagnose based on general sequence of operation.
we need to hear, open hot tap, dhw demand light comes on, pump runs etc etc etc or we will be guessing which is pointless and could be expensive

iain
July 2008