The Sat Nav in my 645 Cab Can't locate were i am.? Every thing seem's to work ok but my arrow locater keeps wandering off position some times miles away from were i am.? It told me to do a U Turn on the M62 last Week...!
I have had this before, albeit in an Audi. GPS antenna had died, OEM kit was around £300-400 from memory so I bought an external GPS antenna on ebay and fitted it in a few minutes. Could be worth checking the antenna itself, any damage, signs of water ingress etc.?