When my 2000 4Runner's temperature dial is set to the coldest setting without AC and not recirculating, I still get air that's noticeably warmer than outside. This is fine for the winter, but it's unfortunate for the summer on cooler nights where I either need to open the windows or turn on the AC on the highways. I also think it might be impacting the effectiveness of the AC on hot days.

I just pulled apart the glovebox and some paneling on the passenger side. The blender door actuator seems to be able to move somewhat freely from hot to cold using the temperature dial. I'd like to open up where the blender door sits to check if there's a blockage somehow. It seems like hell getting enough clearance for tools and taking the box out.

Has anyone had experience in doing this?

Well I think to some degree all vehicles will have that feature. Have you measured the differnce? I think a few degrees has to be normal but perhaps 20 is not.

But there could be other factors at play. Like maybe, just maybe the heater valve is letting some hot water thru causing the increasing in temps. So I'd check that too.

Luck and enjoy the Runner.

Surprisingly, I don't have a thermometer around so I'll grab one and test it out later in the week.

With the old RAV4, the fresh air was a little bit warmer than the outside ambient temperature, but it was definitely tolerable and I almost never used the AC. With this 4Runner, I need crank on the AC even on cooler days on the highway.

I'll see if I can get someone who is smarter than me to check out the problem and probably pull the heater box.

I don't know what your problem is, but it sounds like your pushing hot ari from someplace. I like the idea that it might be your heater control valve not fully closing since you said the heater control doors are working. carefull the heater control valves get brittle with age
work the leaver and see if its going full on and full off

I had a similar observation about the slight residual heating of the fresh air in my old Toyota 4WD truck, which uses a similar design heater valve. Alas, I made no scientific tests. I replaced the valve as a precaution, but always in that truck and now in the 4Runner, when shutting the heater heat off, slide the control all the way to hot, then immediately all the way to cold (off). The idea was to make sure the valve is forced all the way to the closed position through the [presumed] elasticity or slop of the cable and lever control.
These 4Runners are hot vehicles; the exhaust runs right under/alongside the center hump and heats the inside floor substantially.

I'm betting it's the air mix servo being stuck open. It's located behind the passenger floor vent. If it's not working properly them the vent won't close, and you'll have not air all the time.

Mike