South Africa does NOT accept Road Vehicles on a Carnet. If you wish to take a vehicle into South Africa under a Carnet, you must obtain approval from South Africa's government in advance.
The ATA Carnet entry is not allowed for household effects, motor vehicles and any other related equipment entering for the purpose of immigration, contract work or temporary work permits.
The South African customs territory includes Botswana, Lesotho, Namibia, and Swaziland (BLNS States). Although they are part of the same customs union, carnet holders must exit South African borders before entering any of these.