First: the cabin filter. A dirty filter drastically cuts airflow and causes odour, and replacing it is the cheapest thing you can do.
Second: condenser cleanliness. Dust and insects block heat rejection, and the result is poor cooling when stationary.
Third: the cooling fan. If the fan is not running at the right speed, the A/C cools while you drive and gives up when you stop.
Fourth: leak detection before charging. Charging refrigerant into a leaking system means burning money every couple of months.
Fifth: refrigerant weight. The charge must be by weight per Toyota specification, never by guesswork — overcharging is as harmful as undercharging.
Sixth: duct sanitisation. That smell when you first switch the A/C on comes from bacteria on the evaporator, and it is fixed with a dedicated sanitising treatment.
