Chrysler Repair: atc problem, 94 concord, 1994 chrysler lhs, chrysler lhs

Question
I am a novice in car repair but I dont want to get taking advantage of either. Referring back to the question:

http://experts.about.com/q/Chrysler-Repair-807/1994-Chrysler-LHS-AC.htm

this is my exact problem but it all depends on hot it is outside. The hotter it is the more it cuts off. Also if I hit the right side of the panel it sometimes comes on. Is it something I can fix are do I need to order a control head. If I need to order what is the cheapest place and how hard is it to change. Remember I am a novice in this department.
THANKS please,
it is hot enough in Houston w/o the heater on.

Todd Smith

Answer
Hi Todd,
My first thought is to evaluate whether you have sufficient refrigerant in the AC system because you note that it is worse the hotter it is. That would be consisent with a below necessary amount of refrigerant.
If that proves to not be the issue, then looking into the electronics of the control head would be useful. But first it would be important to take advantage of the self-diagnostic capabilities of it. Here what I wrote to another '94 Concorde owner in June of this year:
"I suspect that the ATC head unit is faulty because it doesn't light up and becasue of the loss of control of the air distribution, though it could be a fuse issue also. The blowing continuously may be due to a faulty blower motor module which is located in the air duct to the left of the blower, but I would not conclude that is the problem until the control unit was working once again. The unit does have a self-diagnostic capability. The engine has to be running  to do the test. Simultaneously press the floor, mix, and defrost buttons, (the 1st,2nd and 4th on the top row) and see if the display unit begins to blink. Release the buttons when it has started to do that and then after it blinks for a while longer watch for two digit numbers to appear on the readout. Those are the fault codes. Note the number, then press the "panel" (1st button of bottom row, I believe) button for any further numbers. When all numbers are revealed it will return to normal function. Let me know the numbers.
If the head unit doesn't respond at all, then check fuse #6 under the dash. There is also a 12V supply line to the control that is directly connected to the battery on a black/pink wire on the green plug on the rear of the control unit that should be checked to verify that you are getting that power to the control unit. To remove the control unit use a screwdriver tip to pry the bezel edge gently away, then pull straight back on the bezel surround that conceals the radio and the ATC unit. Then remove the 3 screws that hold the ATC control to the dash structure. I know of no service manual for the ATC head unit, but you might inspect the circuit board for sign of a blown capacitor or other component failure which you may be able to replace with parts from an electronic supply. Otherwise, try to obtain a replacement from a pull-it-yourself wrecking yard."
The ATC head unit electronics is complex and involves a number of sensors as well as the digital data bus and the body computer. I have the wiring diagrams for it. It appears that the underdash air handling housing (including heater core, evaporator core, and air control doors) is identical to that of the conventional unit. At this point in time the most economical source of parts will be to find an LH vehicle of the same vintage at a pull-it-yourself wrecking yard. I can't be sure why hitting the right side of the panel is doing, but you might want to check the plugs and sockets on the rear of the unit and maybe try operating it partially removed so that when it goes wrong you can try manipulating the harness wires to see if one of them has an intermittant connection you could chase down and correct.
Let me know what you learn, please.
Roland