slidekicks

Hi. I have a 2014 Superb Elegance Hatchback and some times the unit will not switch on and the times it does it cuts out. Skoda have had it for two days on test and no faults are showing. The car has only done 8160 miles since new as it was owned by a chap that had bad health and could not drive so was parked in his garage for a few years. Before i buy a new unit has anyone any ideas as to what the problem is please. Thanking you in advance for any help.