What causes the lack of heat in the Vios' heating system?

[Mercedes]

The reasons for the lack of heat in the Vios' heating system: 1. Issues with the engine cooling system; 2. Malfunctioning heating control mechanism. During repairs, it is necessary to first determine which aspect is causing the problem before proceeding with the corresponding repairs. You can check the temperature of the two inlet pipes of the heating radiator. If both pipes are sufficiently hot, it indicates a problem with the air flow control mechanism; if both pipes are cold or one is hot and the other is cold, it indicates an issue with the cooling system. The Vios is a family-oriented entry-level model specifically designed and developed by Toyota for the Asian market. In terms of body dimensions, it measures 4410mm in length, 1700mm in width, and 1490mm in height, with a wheelbase of 2550mm.