Viva clacking alarm when heater turned up to 19 degrees

[Raffajaffa]

Hello. love our little viva low mileage 16k and trouble free for its two elderly owners since new.Ex Vauxhall employee. 
however Suddenly we have a clacking sound from behind or under dashboard.  After a week of it going off when starting the engine or latest just switching ignition on for a few seconds I have discovered that it is connected to switching on the temperature control dial. Bellow 18 cuts off the alarm  no other problems or noises?    Turning up over 18 starts the ac into on. 
  Cannot get car into my usual garage till after new year.  Recently serviced even after 2k miles per year.   Unable to do anything myself.

is it safe to drive albeit short distances.  Any suggestions helpful. Yep I am wearing warm clothes.  Dave

[Vauxhall Owners Club]

Have you managed to discover the cause of this issue yet?
Wondering if it is battery strength being low on start up and invoking the alarm or relays to become active and when AC kicks in the that is more drain on the battery?