Update. I was looking to install a dash cam to my EQV but was not happy with the specs of the Merc cam that could be hardwired/installed by the rep. I opted for a blackvue that has far more features but connecting it to the 12V port means that there is no parking recording when the ignition is off. Hardwiring the camera correctly should have been straight forward but there is very little info available for EQVs. I purchased an OBD cable for the blackvue (connects to the OBD port under the steering wheel) and the camera works fine (with parking mode on). Problem solved.