Assuming everything works on your 4Runner, assuming you have manual HVAC controls, it may seem counter intuitive, but if you turn the fan ON, switch to cold, open the air vent so outside air can get in and turn the knob to windshield defrost vent, this problem should disappear within a couple of minutes. There should be an icon on the vent control - if you look closely, you'll see it says "USE WITH" and points you to use outside air vent when the windshield option or windshield and foot option is selected. The AC will turn automatically regardless if you turned the AC switch ON (you can hear the engine rpm change when idling at a traffic light for example), and will dry the windshield intermittently. The condensation from the air is collected and drained out when it makes contact with the AC evaporator when air is recirculated back thru the vent under the passenger dash or is directed thru the rear trunk vent on the left fender. You can see the condensation drain under the car behind the front right tire on a left hand drive 4Runner.

For this to work, all these should be in good working order:
-The ac blows cold - ac compressor will not start when the car is full of cold air, but will start if you switch to one of the "USE WITH" icons on the left knob.
-the temp select knob should adequately change temp - ask someone to change temperature and observe the heater valve moving located directly under the hood above and behind the motor.
-the outside air vent should be opening without obstruction
-air should blow thru the vent for the windshield located in front of the dash when the fan is on
-the back rear left fender vent in the trunk should not be obstructed.


Having the ac turn on from using the "USE WITH" icons on the vent control, should also help warm up the engine faster as more loads are turned on (ac compressor)

If your Runner has manual controls, that's how you clear the windshield. If you have autoclimate control, someone else please share as non of my 4runner have this option.

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