“At some point last year my car’s air conditioning unit started to develop a bad smell, which is a sign that mold has formed on the condenser. Unfortunately, this part is hard to reach and cleaning the condenser is hence a big problem. I went through a set of commercial climate control cleaning products and found most of them pretty useless:1) Two different disinfectants in spray cans that are sold as climate control unit cleaners: The spray cans are easy to use as you just put them into the car and let them spray their content while the ventilation is running. Unfortunately, the smell was back two days after their application. I guess the sprays are a combination of a perfume (they leave a strong lemon-like smell in the car) and am mild disinfectant like isopropanol. The latter one is not good for killing mold if it reaches the condenser at all. 2) A spray can with a long tube to spray disinfectant and cleaner directly onto the condenser. This is actually a pretty good system and preferred by most workshops due the simplicity and easy application. It actually removes organic matter from the condenser and typically protects it with a good fungicide. However, you have to be able to reach the condenser with the tube which in my case sadly wasn’t possible. It would have meant a lot of extra work to make it accessible. Also, the ventilation shafts are not cleaned by this method. Talking to a mechanic I found out that some workshops use ozone generators to deodorize such cars. They use it also to remove cigarette smells or other unpleasant odors. Due to its gaseous state, short lifetime and exceptional reactivity ozone can reach the radiator, reacts with the mold (killing it) and vanishes without a trace after some hours. As professional ozone generators and cleaning services are pretty expensive, I decide to build a simple ozone generator from cheap available parts.”