Why do my AC and Heater both blow air that feels the same as the air outside? on 2003 Ford Taurus

Started some time in the winter. The heater started blowing air that felt like the air outside. Fortunately the winter was coming to an end and it wasn't a pressing matter, but as the weather warmed up and I began to use the AC, I got the same air I was getting with the heater.

Some notes about operation, and what I've checked thus far:

-Engine runs at normal operating temperature. Comes up to temperature quickly and NEVER overheats (thus ruling out thermostat).

-Both hoses going from the Heater Core through the firewall heat up normally.

-Compressor engages correctly when AC is on max.

-Both high and low pressure readings were normal; refrigerant and anti-freeze are both clean and full.

-Recently performed radiator flush & fill.

-Used the UV crap to locate leaks. Found none.

-Air blows normally from all ducts, and responds to adjustments in fan speed.

-This particular Taurus has the automated/push-button temperature control, not the dials.

My last 3 oil changes and tire rotations were performed at 3 different garages (on purpose). I had all 3 run diagnostics, and none pulled any codes. Each suggested completely different solutions, but none were different than the ones I, or someone else had already ruled out.

I am getting exceedingly frustrated. I have to drive long distances on occasion, sometimes with my two very young children, and I hate trying to improvise climate control. I also have no interest in letting some mechanic tear apart my dash for 6 hours, charge me $800, and then potentially not fix the problem or find it could have been much simpler.

I have yet to find anyone who can explain why both the heater and AC blow the same air, despite them being independent units.

Can anyone help?!?! Thank you!

Asked by for the 2003 Ford Taurus
Tempture blend door inop. ambient or mixed temp. air only. Possible dash hvac control unit, body control module, (should have code) door actuator motor, broken or jammed componets, broken wire etc... Somebody gonna have to look inside the unit to find your trouble!
There have been no codes as of yet, and someone I visited with today thinks it could be the Temperature Blend Door Actuator. I'm trying to find a video guide or something on that right now.
Sometimes youtube will have something but you prob. know that.
1 more answer , 3 more comments
sounds like your blend damper is stuck open mixing too much out door air had same problem with explorer.mine had a broken linkage arm
Since I haven't heard anyone say this yet, I'm going to pursue this option. Any tips or videos of this particular issue? Google and Youtube yield a zillion results that cover a lot of little things, but none specifically to my car model.
found mine on you tube, had to access thru glove box but not too hard. you did not mention if your system was vacuum damper or electric- mine was vacuum
Good question. I'm not entirely sure. I will see what I can find out.

Thanks for the tip!

P.S. I found a video for replacing the actuator through the glove box. That's the one with 4x 10mm bolts, yes?