Rear Aircon fan not working

[Chiggsy]

Hi
Ive just got myself a Caravelle with HVAC has anyone had the rear aircon fan stop working ? If so how did you fix it ?
Ive done the basics ie checked the fuses, Ive also put power to the fan and it works,
Spoke to VW..... apparently there is no relay and it is the resistors in the fan !!!! BUT it works with another power source
Any help would be much appreciated