AC musty smell - evaporator drain location

Hi ! I ended up having your problem and found my way out of it. I'll share it with you.

The evaporator is located in front of the cabin air filter.

(back side) EVAP <- AIR FILTER <- FANS (front side)

You can access it and see it from the filter tray. First, remove the cabin air filter and dust off any debris with a vacuum.

There exists evaporator cleaning cans meant for cars that allows you to spray foam onto it. You should follow the instructions written on the can, but they should be similar.

Wear gloves. Do not breathe the product.

First, spray the front face of the evaporator from the filter tray. You may use a gentle brush (ex: long toothbrush) to ensure that is is coated nicely with foam. Do not push hard, as you can damage the fins.

Unplug and remove the evaporator temperature sensor (circled in red).

Spray the back of the evaporator from the evaporator temperature sensor hole. You can fill the thing (but not too much), the foam expands and should go where you want it to.

Close the filter tray without installing any air filter. There should be some foam left which is wanted.

Let it sit for a few minutes.

Open the windows to limit breathing toxic vapors. You may also open the doors.

Select the minimum air flow on the panel.

Turn the engine ON, and turn the A/C ON. You may want to crank the heat to the max level, as the exiting foam will then go to the heater core and clean it at same time.

The foam from the front face will be pushed through the evaporator by the air flow. Gradually increase the air flow up to level 2. Over level 3 or at level 4, foam will start to spray from the vents. You may want to be be ready for that and prepare towels.

My can does not say how much time you should run the A/C system with the cleaning foam and at which level. It is totally up to you.

You may repeat the previous steps a second time to clean the system even more thoroughly. Do not waste the products as they are toxic.

The foam should collapse and turn back to liquid after some time. It will drain itself from the A/C drain hole and you should not need to worry about it.

Once the evaporator is cleaned and the system dry, put a new cabin filter. You should change it regularly to ensure no dust collects on the evaporator later. You A/C should now more efficiently (better cooling and better fuel economy), and without that nasty smell ! ;)