That smell when you start the AC is not the air freshener's fault

It is biofilm on the evaporator

The evaporator sits behind the dashboard and runs cold and wet. Dust gets pulled onto it by the blower, sticks to the condensation, and organic matter grows in it. When you start the AC, the first rush of air comes through that layer — which is why the smell fades after half a minute and comes back the next morning.

Why fresheners make it worse

A perfume masks the smell without touching the cause, and several of them add an oily residue to the vents that gives the dust something else to stick to.

The actual fix

An antibacterial foam is injected directly into the evaporator housing, left to dwell and then drained out through the condensate line. The ducts get an ozone treatment, and the cabin filter — which is usually filthy and is the cheapest part of the job — is replaced.

While you are in there

It is worth measuring vent temperature at idle and at around 40 km/h. A system that cools fine when moving but poorly at idle is usually telling you about the condenser fan or a gas level, and catching that early is much cheaper than catching it in May.