03 Limited with dual climate controls.
Can anyone help me understand the actual function of the 4 different actuators that I find listed for my heat & A/C?

From left to right I find:
87106D / 8710635170 (Air Mix/Blend) - Determines driver side Temp (replaces 8710635130)
87106J / 8710635120 (Mode)- This regulates where the air comes out: Vent, Floor, Defrost.
87106L / 8710635180 (Air Mix/Blend)- Determines passenger side Temp (replaces 8710635140)
87106G / 8710635150 (Recirc)- Fresh air or re-circulation

Also, if I am replacing my heater core (and pulling the dash apart to do so) are any of these more accessible while I am doing that and worth doing while I am in there?
IIRC the 8710635120 is hard to reach without removing some stuff or drilling a hole somewhere...Are any of the others hard to get to without taking the dash apart?

Thanks!

Attached Images

 

The 3 that are in the drawing together... the 2 on the right are for mode (where air comes out and for air mix (sometimes referred to as "blend") are for temperature for the passenger's side, the other one is also a air mix for the driver's side.

The one by itself in the drawing is for recirculation.

Any the first 3 would be easier to replace when the dash is removed while replacing the heater core, the driver's side is the easiest one to replace if not removing the dash, the recirculation one would a little easier but not by much...BUT I would also highly recommend replacing the AC evaporator that's in the same housing with the heater core, if the evaporator ever starts leaking in the future you will be doing the same work all over again to replace it, which is a big job and the cost of a new evaporator isn't all that expensive.

I updated the first post with additional part numbers and the correct functions I think.
Look good to you?

Would you say that all but the 87106J are reasonable to do with the dash in?

That all seems to be correct, none but the driver's side are easy if not removing the dash but yes 87106J is the hardest with the dash in place.