Water Content Of Refrigerant R744 (Carbon Dioxide)

WARNING: This page is about a different car, the 2022 Volkswagen ID.4 and 2021 Volkswagen ID.4. However, it is still accessible from the selected car via links, so may be relevant.

Only very small amounts of water are soluble in liquid refrigerant. On the other hand, refrigerant vapor and water vapor mix in any ratio.
Water destroys the A/C system, because it can form acids when combined with other contaminants at high pressures and temperatures.
Any water in the refrigerant circuit will be entrained in droplet form once the desiccant bag (in the accumulator) is saturated (it has absorbed as little as approximately 7 grams of water). This water flows up to the restrictor nozzle and turns to ice, and the A/C system no longer has a cooling effect.
Depending on the refrigerant circuit design, this may also result in certain A/C compressor regulating elements freezing up, causing the A/C compressor to no longer be regulated. For example, if there is water on the A/C compressor regulator valve and it turns into ice, it can lead to various complaints, depending on the A/C compressor design (either the A/C system stops cooling, or it cools so strongly that the evaporator ices up).