Would you have any clever ways to further test the actuation doors being the issue in system?

IIRC, I do have some extra pinouts I wired in a long time ago that allow me to manually control my actuation flapper door. Its been a VERY long time since I have used them, but they are there and when I tested actuating the door manually when the dash was out the actuator moved as expected, and when I would manually actuate the door with the dash in, it did not seem to help increase heat output. As mentioned above, I can't physically see the door opening but when tested before it worked fine, and I have never had any change in maximum heater output.

Thoughts along that line, is it possible that "outside air" is being mixed into the HVAC instead of cabin air helping to increase core efficiency? Wild thought but looking for a path to test and see if I can repair this sorry missed system.
The foam on the HVAC assembly was reasonable, nothing too bad when I had it open, but I recall lots of HVAC systems I have seen loosing the foam on the door flappers that helps seal. Grasping at straws...just looking for ideas.

 

Do you know how the HVAC system physically allocated heat per blower setting Dale? Which doors are open what target percentages at what times? I do typically use this far CCW setting, I will be explicitly testing the "lower vents" (12 O clock) setting and see if it changes anything or even makes a noticeable difference in temperature output.

Commented above, I think the damper door does work (pretty sure that's still true, its been a long while), and I even have extra leads I added to actuate it manually with the dash in if needed, but every time I have been able to physically see the doors, they physically actuate in the assembly, as well as I have manually actuated the door and unplugged the HVAC plugs then heated the car up completely with no change to output from the HVAC.

I know FD heaters are a bit subpar based on lots of feedback here, but this one in particular has always literally been lukewarm for heat output. The temperature that comes out of the vents is so mundane that even when its very cold/freezing cold outside its barely perceivable that it is working. On a warm night it feels cool on the hand with the car completely warmed up and if I give it gas, what little heat is in the HVAC air disappears as the radiator core gets more airflow and you can feel the temperature of the blowing air decrease nearly instantaneously.

I have read a few reports of people that say their FD heater blows "hot", like this guy that brought his back seemingly from being completely clogged with block seal
> I have nuclear heat and no leaks.
https://www.rx7club.com/3rd-generati...0/#post8821205

 

All I can suggest are the troubleshooting guides in Section G of the 1994 Body Electrical Troubleshooting Manual. See Flowchart 5 in particular. Also, search this forum for some good discussions on how to check the air mix actuator function and rebuild or replace it.

Just to be clear, the heater has 3 different actuators (source, mix and mode) and their associated damper doors - one for the source air (Fresh/Recirculate), one for air mix (temperature) and one for the output mode (clockwise: dash only, bi-level, floor only, defrost+floor, and defrost only). Using recirculated cabin air instead of outside air as the source would make some difference in how quickly the cabin heats or cools, and when it is very hot or cold outside, recirculate helps the cabin reach a cooler or warmer temperature than it otherwise would. The output mode also makes a difference in cabin temp because it not only directs the blower output to your defroster, floor or dash, etc., it also works somehow with the air mix damper, depending on the setting, to blend in some untreated outside air. This is noticeable from the dash vents when the mode switch is in the second or bi-level position. Such blending should not occur in the other mode positions. So, I suppose weak heat output could be due to 1, 2 or even all 3 actuators/dampers not working correctly, but the air mix is the usual suspect.