Early build Volkswagen cars can experience a power drain issue after upgrading their 2nd generation headunit from a RCD 300 or RCD 500 to a 3rd generation headunit like the RCD 210, RCD 310, RNS 310 and RCD 510.
The problem is the CAN bus Gateway is too old and an updated version 1k0907530 (1k0 907 530) of L revision or higher is required - CAN bus gateway removing, installing and upgrading – Volkswagen Golf.
Vehicles belonging to the model series PQ35/PQ46 from model year 2008 (MY08) as well as the Tiguan have gateways that are updated. Earlier models may require the updated CAN bus gateway to be installed. See Volkswagen Model Year Information for more details on the week of manufacture however generally Volkswagen change over Model Years around Week 22.
This problem does not* affect retrofits of the RNS 510 which is a 3rd generation head unit as this unit was in the production in 2007 whereas the RCD 210, RCD 310, RNS 310 and RCD 510 are recent additions.
Check the ‘Skoda Parts’ link (right hand menu) for a reasonably priced gateway. Revisions that will work after the 1K0 907 530 S (1K0907530S) revision include 1K0 907 530 AA (1K0907530AA), 1K0 907 530 AB (1K0907530AB) and 1K0 907 530 AC (1K0907530AC).
* This problem does now affect the RNS 510 if the firmware is upgraded to 2660 or higher. The RNS 510 will exhibit the same problems as the RCD 210, RCD 310, RNS 310 and RCD 510 and requires the CAN bus gateway to be upgraded.