You'll never guess what! I went out yesterday with my twin baby boys in the GT4 to Costco! They have some great car stuff deals! Mobil 1 0w-40 for 29 quid all in for 5Ltr. Plus a fantastic tool box thats massive! Really want Santa to bring that for me! Lol... but I digress! Went to Maplins and bought some electrical contact spray ready to have a go at the conections! Started the Mrs car up this morning to get the Webasto heater on! And Hey Presto! As if by magic! The heater fan is working again! Happy days. So it has to be a lose/dirty conections as you said