Personal observation about the HVAC system and the mildew odor

The Tacoma is the first vehicle I've owned where it was advised to "dry the evap coil" by turning off the AC a few mins before arriving home each night (but leave the fan running). But even with this practice, I would occasionally get the mildewy smell from the evap coil basically staying wet overnight. A year or two ago I used the FJC coil cleaner stuff in the can to really scrub the coil and that got rid of the funk.

(I have confirmed that the drain tube is clear)

For some reason, this summer I got a hunch that using the fan on HI speed (#4) creates a lot of turbulence in the vent system. In other words, I always felt it made more noise than it actually pushed that amount of air through the vents. (the vents on the Taco seem kind of small too)

Well I ended up limiting the fan speed to setting 3 and as a result I have not had any mildew odor issues all summer (knock on wood). If I were to guess, something about the air flow on this setting helps the evap coil drain to work as intended; whereas the HI setting might be causing the liquid to splash around all inside the box and maybe get caught in nooks where it can't ever dry out properly.

Just my .02 in case it helps anyone else

 

Interesting, I've yet to have this issue and my blower lives on high 90% of the time for 9 months of the year.

I do turn the A/C off for a few min before I park it for the evening and also clean the cabin filter (K&N) pretty often.

 

Interesting. While I don't think my truck smells like mildew, it does have a smell I'm not too happy about. So far no amount of cleaning has been able to get the smell out I always attributed it to the prior owner having dogs in the truck all the time (something I wasn't aware of until I removed the seats and some other panels to do a deep cleaning). I wonder now if the AC could have anything to do with the smell.

 

The FJC coil cleaner is cheap enough to try. I found the best method was to actually unscrew the blower motor (just 3 screws if I recall). You can then snake the tube up the hole and directly into the box where the evap coil resides. Then just foam the heck out of it and let it drain.

$19 FJC 5914 Foaming Evaporator Cleaner - 16 oz.

https://www.amazon.com/FJC-5914-Foaming-Evaporator-Cleaner/dp/B002EAKX88?sr=8-1

 

No smells from mine, but FWIW, my 2014 also makes strange noises when the fan is on "full high" as well. It doesn't seem to be the fan itself but rather some resonance behind glove box and head unit all the way to across to the left to the right-middle vent right center vent. Consequently, I don't use it much (4) except for quick cool-downs on re-recirculate. Mine also runs cold enough that I can usually maintain the cabin at a comfortable level on speed 2 or 3.

 

I think this is an issue with most vehicles. A few things to keep the mildew smell from coming back.

You can use this. Just insert in the ac drain hose that exits the firewall.

Lubegard 96030 Kool-It Evaporator...

$13 Lubegard 96030 Kool-It Evaporator and Heater Foam Cleaner

https://www.amazon.com/dp/B0007PHD0S?ref=ppx_pop_mob_ap_share

You can spray lysol on the plastic cowl molding outside of the vehicle with the ac on and the button pressed for outside air.

Install a new cabin filter.

 

Sticking the tube through the firewall drain will not work on these trucks. You can prove this to yourself by pulling back the carpet in the passenger footwell and seeing just how kinked/turned the actual hose is. (I think this also contributes to the mildew issue because water has to travel so far just to get out of there, and then if you happen to park on an incline then the odds of it draining out becomes much less)

When you stick a flexible hose in through the firewall tube, it'll go in about 6-8" and then hit an abrupt stop which is the first 90 degree turn of the hose. If you then inject foam at that point, barely any of it will travel further up into the evap box and coat the actual coil.

 

I did this exact method on my 2nd gen tacoma. Get yourself a small container. Then pull the tube on the passenger side into the cab. You will be able to work the flexible hose through the bends. Then push the tube back through the firewall. Anything at this point is worth a shot. I hope that helps. If not someone else will chime in soon. Tw is probably the most help forum amongst members. Best of luck

 

I wouldn't think so as the air from the blower helps force the condensate out, if you put your hand in front of the drain with the blower on you will feel the air coming out.

Some of it may have to do with the environment as well, different areas may have different stuff floating around in the air.