* Low refrigerant level: If the refrigerant level in your car's AC system is too low, it won't be able to absorb heat effectively, resulting in hot air blowing from the vents.
* Faulty compressor: The compressor is the heart of the AC system and is responsible for compressing the refrigerant gas. If the compressor is faulty, it won't be able to generate enough pressure to cool the air.
* Clogged condenser: The condenser is a heat exchanger that helps to dissipate heat from the refrigerant. If the condenser is clogged, it won't be able to transfer heat effectively, leading to hot air blowing from the vents.
* Faulty expansion valve: The expansion valve controls the flow of refrigerant into the evaporator. If the expansion valve is faulty, it won't be able to regulate the refrigerant flow properly, resulting in hot air blowing from the vents.
* Electrical issues: Electrical problems, such as a faulty AC relay or a blown fuse, can also cause the AC to blow hot air.
If you're experiencing hot air blowing from the vents of your 2005 VW Passat, it's important to have the problem diagnosed by a qualified mechanic as soon as possible.
