Ferroli F24B Combi Boiler. Follow on to earlier enquiry?

Hi DC, or whoever else can help me, PLEASE? Following on from Gemma's enquiry, i too have a Ferroli F24B combi which will supply hot water on demand, but will not supply the central heating system (just stopped working!!!). I've followed DC's advice and completed a full reset on the clock, with all of the switches in the appropriate positions (still didn't work). I then, as DC suggests, joined the two black wires labelled 3 & 5, and the central heating works. ("don't forget to turn off the electricity to the boiler before removing the cover" great advice!!!). This is obviously a very short-term fix, but if the central heating works with these two wires (3&5) connected (or hotwired), does this mean that the DIEHL timer/switch unit is knackered?? Like to add at this stage that the clock and all of it's functions seem normal. Many Thanks in advance for any help you could offer. TA