Ok so, here is the link to another thread that was from 2012, but probably becomes more relevant as 3gens get older.

Passenger is FREEZING!

The problems: Your girlfriend/wife/lover etc constantly complains... that her feet are cold! You put the heat to HELL and fan power MAX, but then you start sweating your balls off! This usually happens when you have closed off outside air. When you put the fan to ON, it may or may not help. But then the windshield fogging starts which is major annoyance too.

The problem arises from the heater unit's vent valve that regulates internal/external air circulation which moves forward and backward relative to the vehicle.

When you want to close off outside air, the vent valve moves forward (either manually or electronically, depending on which model 4Runner you have) and compresses a foamy heat resistant seal, sealing the vent to outside air.

Same thing happen when you want to open outside air to come in. The valve moves backwards and presses another seal closing off the cab's front re-circulation vent.

Over time these two seals age and dont make an air tight fit.

Adding to that, the lever that moves the vent valve in either direction can also wear out and not managed to move the vent valve all the way to compress the already squashed seals and outside air starts to seep in, bypassing the heater unit radiator by seeping in through the cab's front vent and directly falling on passenger's right foot pinky toe!
Now we know how sensitive this pinky toe is!

In really cold winter, I made my girlfriend drive me around and my whole right leg froze to the knee, while my left leg was hot from the lower left vent located on the passengers side.

Anyway, it will come a time that you will have to fix this. It is not the most lazy job, but the effect is worth it. Make sure you put a good quality new seal when you start fixing it.

PS, the air vent chimney, located under the grill in front of the windshield wipers, is not very tall. So when parking the 4Runner, makes sure that the car is not tilted to the right. In heavy rain the rain water can overflow this height and start pouring by the gallons inside the heater unit and soak everything in the rights side of the cab! Especially if the waterway inside the left fender is blocked by leaves and gunk.

Hope this helps

credit for pics - some ebay offer used as reference

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Do you have a write up of how to fix the issue?

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I believe that when you pull the heater unit, all you have to do is replace the foam with a new one. Look to buy a heat resistant one, preferably.

It's not hard, it is just a lot of taking apart. You have to take out the glove box, remove the fan, maybe remove airbag, not sure.

Fixing the lever that moves the valve itself, may involve pulling one out from a junkyard and replacing the worn out one. Or fabricating some fix.

That's all I have. Mine hasn't started doing it yet, but my dad's 4Runner is.

Thanks for the tip I'll have to check it out. Originally I thought I had a hole in the firewall that was letting cold air in the passenger's side.

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Not heater related, but more mystery cold air..... but it's been a conversation between a few local buddies.

Anyone know where that wave of cold air comes from when you take a turn? Most of us talk about feeling it when driving and taking a turn through an intersection. The whole cab gets a wave of cold air. I would say a door seal due to the amout of air.... but my seals are good (except small damage on the bottom from my feet, from getting in and out).

Anyone else in the winter time feel this?

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Doesn't get cold enough to feel is here... but how is your rear vent flap? Behind the driver's side bumper corner...



-Charlie

Good question. I've looked it over briefly but since it was in the back, it didn't "feel" it was coming from that direction. It does seal pretty tight and seems to only open when a door closes (as it should to release pressure), but I maybe it's breaking seal as the body twists going around a turn? It's worth inspecting the seal closer when I get back home....

Thank!

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