Why Your Car AC Smells Bad — and How to Fix It
That musty smell when you switch on the AC is bacteria and mould in the ducts. Here's how to clean it yourself.
What causes the smell
Moisture from the evaporator combined with trapped dust creates a breeding ground for mould and bacteria deep inside your AC ducts. The result is that damp, musty odour every time you start the AC.
Foam duct cleaning, step by step
With the engine off, shake the AC foam cleaner, insert the extension tube into the vents and spray so the expanding foam reaches deep into the duct channels and evaporator, breaking down deposits.
Flush and refresh
Let the foam work for 10–15 minutes, then start the car and run the AC on fresh-air (not recirculation) for several minutes to flush everything out and dry the system.
Keep it fresh
Run the fan on fresh air for a minute before switching off to dry the evaporator, and clean the ducts every few months to keep cabin air healthy and odour-free.
