Aircon Evaporator Clean

[rovertone]

Can anyone please advise me on the correct way to disinfect the aircon evaporator?
I have had two goes once last year using a Wurth brand product I followed advice and using the extension tube sprayed up the drain tubes albeit I couldn't get the tube past the point where the drain tube goes thru he body. Consequently most of the disinfectant poured back out and was a waste.

My local aircon specialist said I should remove the pollen filter and spray in thru the intake. I did this today but the flap only opens with the fan running so did this on auto, econ and recirculate, the fan blade spinning restricts things a bit so I also switched off and pushed the tube down thru the closed flap and sprayed. I also sprayed into the drain tubes with same results as before.

I left the fan running for a while to hopefully circulate and dry out the cleaner but I am not convinced I have done the job correctly. I was sort of expecting to see some cleaning fluid run out thru the drain if it had got to the evaporator. At the moment the smell is not noticeable but it does go after the aircon has run for a while anyway.

Just wondered how others have tackled the job and with what success.
Cheers Tony