Okay, my son's got the car and he's 2 hrs away, he's coming home next week so I've got a chance to work this. He's closer to the mountains (frost) than I am, so I'm concerned about it with winter approaching Here's what I know:

- input and output of the heat exchanger are hot suggesting it's not heater core blockage
- the solenoid on the left and right side move when adjusted
- there's no hot air high, middle or low
- there's a minor "fart" of warm air when it goes to defrost, but it cools down to ambient quickly

So I think the flapper inside the box is broken somehow. Any thoughts on the next move? I plan to air blast behind the console to make sure there's not blockage around the core. Other than that, not sure what to do. My biggest concern from a safety perspective is to get the defrost working. I'm happy to cut into the console to direct the air permanently to defrost if that's what the problem is...

Thoughts?

There are two things that need to happen to make warm/hot air come out of the vents (assuming good coolant flow is possible through the core...) - the valve on the firewall needs to open, AND the blend door needs to force air through the heater core instead of around it.

Step 1 is to check the valve on the firewall (in the engine bay) is moving from cold to hot with the dash controls, then next is to check if the blend door actuator is working (for 01/02, even the 'manual' AC 4Runners had actuators instead of cables).

I don't have an 01/02, so somebody else can hopefully provide pictures of where to look for the blend door actuator...

-Charlie

The blend door actuator is in the passenger footwell in my 2001 4Runner Limited. Refer the post here:
https://www.toyota-4runner.org/3805018-post4.html

Oh no!! I just realized the car is a 2004 and a different Gen...so sorry all!

That being said, does the 2004 have the valve on the firewall? Moving to the next gen...