Mold Smell

Mould growing on the AC radiator (aka evaporator?) in the dash would be my first guess. If you use AC a lot, turning it off some distance before your destination but leaving the fan going, gives the condensation a chance to evaporate. Otherwise, it’s easy for mould to start.

 

I used the Toyota Refresher Kit from Amazon. It works great. Got rid of the horrible smell.

 

Replace the cabin air filter.

Pull the panels in the hatch and check under the spare tire and in the side panels next to the rear tail lights for moisture too.

 

Diablo has the answer. It is so common Toyota sells a kit for it. Typically it requires access under the car where the AC condensate hose drains water. After taking out the cabin filter you inject the cleaning foam into the condensate hose where it foams up the AC evaporator coil. Read the instructions.

This problem is most common in the spring after a long period without AC.

 

my HVAC system is always in manual mode with the fan always turning in low (one bar). This prevents the system from forming mold. Just redirect the air flow if it bugs you.
Also check the hatch area and power cord storage for dampness.

Hope this helps....

 

^ If you live where temperature and humidity often compete with each other to reach triple digits this is a good policy.

I've learned to do this in all of my (GMC) over the years even though A/C mold is less of a 'thing' with my personal vehicle than it was when I had my two company Priuses.
Of course my company's fleet supervisors would not even think about using some Gucci HVAC foam treatment.
Their solution would be to just not use the A/C if you don't like the smell.

A couple of times every summer I would park the car in the sun with the heat on when it was 110-degrees outside for a while and I bought and replaced the cabin air filter myself a few times.
Towards the end of my time driving Priuses for a living, Big Bell decided it was cheaper to just let Toyota's service center service the cars - which was much the same as putting two scorpions in a glass jar.

Needless to say, we didn't get the "HVAC treatment" THEN either...........

 

Maybe someone, someday will address the problem, come up with an evaporator that's much less prone to retain moisture, maybe coupled with something that actively dispels it, some sort of heater. Or hey: zaps the area with UV light for a few minutes.

 

Almost all cars in humid environments can do this especially when the AC has not been used for a month or more. Even home AC will do it occasionally.

The foam works well and is pretty easy. It is so much easier than an oil change, it’s a no brainer. One treatment every two or three years and you are good.

Uv does eliminate the problem in home ACs as does 4 or 5” media filters.

 

Maybe something that would vibrate the evaporator when the vehicle's shut down, knock most of the water droplets off? And/or make the evaporator accessible, without needing to completely tear open the dash.

Just dreaming...

 

Maybe the lithium battery retrofit guys should make a drop in uv-c light that installs through the cabin filter slot. It would need a door switch to prevent eye damage.

Of course, anyone who can take a weekend every 50k miles to clean their egr cooler could take thirty minutes every two years and clean their evaporator.



Honestly a few more brake booster rebuilders besides Hybrid Pit would be more valuable. Perhaps with an app that would load the proper software, the big stumbling point that requires rebuilding of your specific assembly.

 

The method shown in the video using Lysol on the air intake worked for me. Keep the fan going for five minutes after spraying. Turn off the AC and run the fan for another five minutes.

Just to make sure, I did it twice in 48 hours. And I do it every 2-3 months for prevention. Also, the advice given in another reply is important- five minutes before arriving home/destination, turn off the AC and turn up the fan.