I just bought a 96 Aerostar as a stable mate for my 95. Been checking it out and noticed that the AC doesn't get as cold as it should and the heater doesn't get as warm as it should. The temp control **** doesn't work smoothly and it seems like the blender door is hanging up. I found several crayons stuck in various places in the van and am wondering if one could make its way into the box that holds the blender door. If so, how do I get in there?!
ALSO, no matter where the function control is set , air only comes out of the vents. Tried to find vacuum hose pulled off in the engine compartment but couldn't. Could the control be bad? I'm assuming this is 2 separate problems. I could sure use some help! Winter is coming!

 

It's possible that crayons or other stuff have fallen down the defrost vents and jammed up both the blender and diverter doors. One way to get at the air box is to get in from the back side, where the heater core is. You need to work under the glove box to remove the back panel. I think I ended up dropping the lower part of the dash panel to get more access clearance. You will probably have to remove the core to get into the air box. That's a separate adventure, discussed many times on this forum.

 

the temperature blend door is located right behind the heater core



AutoZone.com | Vehicle Selection - Year



heater control unit, vaccum operated
AutoZone.com | Vehicle Selection - Year

 

do you have electronically controllrd temp. door. If yes, pull cotroll panell and try to measure voltage on temp. variable resistor. it should be from 2 to 11 V depending on **** position. May be resisitor is worn..

 

My recent -90 3L had similar symptoms when I bought it 4-5 years ago.
I replaced the heater core and while I was in there I checked all I could get at. It turned out the top of the blender door was broken. It is made of plastic. All vacuum parts worked well, but blender door did not move and just a little and cold air would blow from vents only.
Access from the top of the dash by unscrewing all screws close to the windscreen. The vacuum hoses and vacuum motor for the blender door is visible from the top and the bowels of the Heater Monster from the empty heater core space.
I ended up making a replacement part from a drumstick,....(!)
I will have to make illustrations to explain the process, but it is not rocket science, so you will figure it out if this is actually your problem.