How do you DIY IHKA cleaning to remove bacteria & fungi & dirt and improve the system function?

Especially the older E32/E34 like my 11/88 750 without the aircon filter need regular cleaning of the system. I am interested to know how you do it.

Usually I use one of these aircon foam cleaners. Condenser is relatively easy to check and clean -if necessary- after removing the front bumper and maybe the kidney grill. Drain holes of the IHKA unit to the floor to be checked also, they are left and right of the center console on the IHKA box and the moisture drops usually left and right on top of the transmission.

What about the evaporator? That is the most difficult item, as a lot of dust/dirt sticks there. And even difficult to see the result after cleaning. Last time I removed on the center console the left and right carpet cover, removed the heater sword and sprayed there from the rear near firewall.
Then a friend showed me to remove the temperature sensors on the IHKA box left and light, let the aircon run and spray thru these hole with running AC the foam, that means 1,2,4. There are five temperature sensors in the system.
1. Passengerside heatercore temperature sensor, 2. Driverside heatercore temperature sensor, 3. Controlpannel temperature sensor, 4. Evaporator temperature sensor, 5. Outside temperature sensor

After dispensing the product, I wait 20 minutes for product to clean the system. During this time I re-install all components. You will also notice at this time that the foam product with dirt will be draining from underneath the car. The cleaning solution will drain through the drain tubes of the evaporator housing. After about 20 minutes I open windows to allow fresh air to enter the vehicle. Then I turn on the fan to maximum setting with A/C setting in ON position for approximately 1 minute to dry the system.

Or is it better to start the engine and spray the foam below the windshield where the outside airflaps of the IHKA units are? see last pic in above link

In this link somebody is using a garden sprayer on an e90 328i, basic idea could also be used for our model text copied, in the link are pics too: quote
Things I bought:
1) Garden Sprayer.
You can buy any sprayer or reuse the one you already have. I bought 1/2 gallon from the Ace hardware. If you buy - buy the smallest one you can. The space will be limited. Also, buy the one with flexible sprayer hose. You most likely will need to bend it in different directions as you spray in order to clean as much evaporator surface as possible.
2) Some detergents
I bought lysol and pine sol. Lysol at the picture actually doesn't have nice smell. But I used is since I bought it. I also thought - if I don't like it, bacteria shouldn't like it either. I used lysol first, and pine sol next. Still lysol smell remains. So if I did it again, I'd use one more bottle of pine sol after the lysol, or skipped lisol completely. You should, probably, use whatever cleaners you prefer. Not in the pictures, but I used gloves and protective glasses. Do this outside or in well ventilated area.
The hose that goes to the evaporator is behind the glove box, closer to the console, precisely where the blower motor used to be. At the picture you see sprayer's hose inserted in the position ready to spray. Use whatever concentration and total amount you like (water + cleaner) and pressurize the sprayer. I used hot water in a hope for better effect. Lysol I used was of higher concentration than pine sol. Both build some foam as result of spraying. I was afraid this would produce lots of water on the inside, but it only made mess outside the car, and you can reduce that by putting some catch can under the car. Place the sprayer in the foot-well. Put some towel inside the foot-well just in case. Make yourself comfortable, research the hose leading to the evaporator as much as you feel necessary to clearly understand the direction and depth of spraying. Insert sprayer's hose in the direction of the center console. Start spraying just enough to verify the drain hose of the evaporator is not clogged. I did that before, so I had some confidence that the liquid will drain. Still does not hurt to check - look under the car - you should see liquid under the car. If you do not, I wouldn't continue as there's high risk of flooding the inside of the car. I had zero liquid inside the cabin, not even a drop - so all the liquid should drain under the car. From this point on, - just refill and spray in different direction/depth. I let it stay and soak for 5-10 minutes between spraying to let cleaners work on bacteria. It took ~10 minutes to remove the blower and 10 minutes to install it back. The spraying itself took 1.5-2 hours, just because I wanted cleaners to be in contact with the evaporator for more time. As a result there was a lot of liquid under the car. Lots of cleaner smell. I suggest you do it outside or at least put some container under the car to catch water. I had to water the garage afterwards and still there is still a lot of lysol smell. I've mentioned - the smell is not pleasant, so either use more pine sol after the lysol, or skip lysol completely. By the time I started using pine sol I inspected the water under the car and noticed a lot of white substance and particles in it. Could be deposits of aerosol sprays I used before, or who knows what it was. At the second picture you can see white areas at the floor where cleaners drained. Check if you have any leaks inside the car as you spray. If you notice something - I wouldn't continue as you can cause some shortage. In my case everything was dry inside. After I used both bottles of cleaners I assembled the blower and the panel back in the reverse order. That was easy. Started the car - everything worked - ventilation system, radio and all other systems. I was a little scared to spray this much water in the car, but looks like evaporator case is pretty isolated, which is as it should be as there's lots of moisture there during operation. So I started the car and drove it for some time with fan and heater on. No smell of bacteria and lysol +pine sol smell is much better and natural that of those chemical aerosol sprays I used before. So far so good but I will do this again in a little while just in case. This whole process isn't very difficult and I'd rather repeat it pro-actively than smell bacteria again. unquote