HVAC Questions - 2025 SR5

[hikeskico]

Hey everyone. I wanted to see if anyone else has noticed a couple of things with the HVAC on the 2025 SR5 with the manual controls.

Musty smell from the A/C
I’m in Colorado, where it is usually pretty dry, but I am getting a musty or mildew smell from the A/C when the truck first starts up. It does not happen every single time, but often enough that it is noticeable and sometimes stronger than others. I usually leave the A/C on with recirculation when it is warm out. I have about 2,500 miles on the truck and have owned it for around two months. I have never experienced this issue in other vehicles with the same usage habits, so I am curious if it's a 4Runner issue or if it's isolated to me.

Fan speed when using the heat
On the colder mornings we have had so far, I have noticed that the fan speed seems much lower when the heat is on full compared to when the A/C or cool air is selected. Since the SR5 has manual controls, I always assumed fan speed would be the same no matter the temperature setting. This is the first time I have had this happen on a vehicle, so I wanted to see if anyone else has seen the same thing and if it is normal behavior.

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[Nodak]

from what i have seen especially from my wife's vehicles, the musty smell mostly happens when you run the a/c whether intentionally or via defrost/windshield mode (either one of those will run the compressor and feed conditioned air whether the a/c button is pressed or not) and not turn off the a/c and let it air out via fresh air.

she tends to run the a/c and just shut off the vehicle. when she or i get back and start the vehicle you can smell the musty smell. this was really apparent in our 2023 tundra when she first got it.

i have a habit since my 2014 4R to always turn off the a/c once i enter my sub division. then i switch it to outside air and turn the fan speed to at least 3 bars to air out the system.

not sure if this a toyota thing but its what i have been doing since the 1990's

as far as fan speed, the only thing i can think of is fan speed on heat may be throttled until the engine warms up. you really are not moving any warm air until the coolant level raises to temp to actually give you warm air.

i know in winters in ND, its really not advised to turn your fans on until you get the engine warmed up when its -10F interior wise. different story if you have remote start but other wise really pointless when your coolant is -10F and the interior is -10F and your fan is just blowing -10F air until.

 

[127.0.0.1]

do you keep it in a closed garage ? this problem happens more on garaged vehicles.
those kept outdoors, super rare to have A/C funk

turn off recirc and run it on outside air the last 5 minutes of driving is a good idea
to prevent this

Toyota has kits (and other places have 'em) you can foam out and defunk your
A/C system if it is really problematic

A/C drain line down by the footwell, check it to make sure it's free flowing

 

[hikeskico]

Thanks for the suggestions. The 4Runner sits under a carport, so it has plenty of exposure to fresh air. I’ll try turning the A/C off and switching recirculation off before parking, but I’ve never had to do that with any of my previous vehicles (Mitsubishi, Chevy, Saturn, Subaru). If that ends up being the only fix, it would be a bit disappointing. I’d prefer not to have to think about doing that every time I drive. I’ll also check the A/C drain line.

Regarding the heat fan speed, the reduced airflow happens regardless of engine temperature. I understand that on cold mornings, you’ll get cold air until things warm up, but even once the system is warm, the fan output is still only about one-third to one-half as strong on max heat compared to max cool with the same settings (top vents, recirc on).

 

[Nodak]

Thanks for the suggestions. The 4Runner sits under a carport, so it has plenty of exposure to fresh air. I’ll try turning the A/C off and switching recirculation off before parking, but I’ve never had to do that with any of my previous vehicles (Mitsubishi, Chevy, Saturn, Subaru). If that ends up being the only fix, it would be a bit disappointing. I’d prefer not to have to think about doing that every time I drive. I’ll also check the A/C drain line.

Regarding the heat fan speed, the reduced airflow happens regardless of engine temperature. I understand that on cold mornings, you’ll get cold air until things warm up, but even once the system is warm, the fan output is still only about one-third to one-half as strong on max heat compared to max cool with the same settings (top vents, recirc on).

it has happened on rare occasions from posts across various toyota forums i have been a part of, but it could be a loose, disconnected or pinched/blocked vent flap restricting air flow.

try using other vent modes and listen for the actuator to move the flaps if you can hear it.

 

[Soloflight]

To avoid the musty smell in any car, turn off the ac 2 mins from your destination but keep the fan on, so it will dry up the evaporator

 

[127.0.0.1]

Thanks for the suggestions. The 4Runner sits under a carport, so it has plenty of exposure to fresh air. I’ll try turning the A/C off and switching recirculation off before parking, but I’ve never had to do that with any of my previous vehicles (Mitsubishi, Chevy, Saturn, Subaru). If that ends up being the only fix, it would be a bit disappointing. I’d prefer not to have to think about doing that every time I drive. I’ll also check the A/C drain line.

Regarding the heat fan speed, the reduced airflow happens regardless of engine temperature. I understand that on cold mornings, you’ll get cold air until things warm up, but even once the system is warm, the fan output is still only about one-third to one-half as strong on max heat compared to max cool with the same settings (top vents, recirc on).

I keep my toyotas outdoors, and on many Toyota forums over the years
people have been reporting a/c funk, clogged drains..etc.
Yaris, Tacoma, 4runner, Rav4...every forum has stories...

So, I kinda get paranoid 'well it's gotta happen to me eventually'
but it never has happened to me, and I don't treat anything special.
I use cabin air filters and ...just use the system w/o a second thought

So, I wish there was some solid correlation about what user actions will cause it and
what will prevent it. Obviously condensed moisture growing mold* is the cause...but I don't have a true answer other than garage kept can make the problem worse for some people due to stable temps and lack of total 24hr air circulation when sitting

*or rodent invasion

 

[Nodak]

I keep my toyotas outdoors, and on many Toyota forums over the years
people have been reporting a/c funk, clogged drains..etc.
Yaris, Tacoma, 4runner, Rav4...every forum has stories...

So, I kinda get paranoid 'well it's gotta happen to me eventually'
but it never has happened to me, and I don't treat anything special.
I use cabin air filters and ...just use the system w/o a second thought

So, I wish there was some solid correlation about what user actions will cause it and
what will prevent it. Obviously condensed moisture growing mold* is the cause...but I don't have a true answer other than garage kept can make the problem worse for some people due to stable temps and lack of total 24hr air circulation when sitting

*or rodent invasion

well sitting outside the wind will force itself thru the vents (however little it is) whether you notice it or not.

 

[mcnuggs]

I don’t know if the SR5 has this option, but my TRD pro has a button that will turn rear HVAC on/off. I’ve noticed that disengaging that (I.e you want airflow to the back), then physically closing those rear vents will create better air flow in the front.

 

[Soloflight]

Yes there is, but manual knob

 

[127.0.0.1]

SR5 is old-skool

Higher trims have the same thing, a manual knob in rear

but if you can select S-flow on the A/C, it will only operate front seat vents
and not operate the rear while in S-flow mode

 

[Nodak]

I don’t know if the SR5 has this option, but my TRD pro has a button that will turn rear HVAC on/off. I’ve noticed that disengaging that (I.e you want airflow to the back), then physically closing those rear vents will create better air flow in the front.

its only on the higher trims do they have a button to turn off rear air flow. the bourgeois have to manually do a reach around for that same effect

 

[4Runner13]

Mike does the same thing with the airflow. Noticed this morning.

 

[Timmybung]

Mike does the same thing with the airflow. Noticed this morning.

I've been noticing the same thing lately on my Trailhunter.

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