Air Conditioning Temp Problem

Can anyone tell me if it is difficult to replace the interior temperature sensor (near the interior light) on a 1986 190E 2.3.
Is there a written procedure some where or is it easy enough for a online description. Is there an easy way to test the sensor before replacing it. My heater will heat very well and cool very well but there is no control. To get the air conditioner to work I push the button above the * button on the control panel and it turns the air conditioner on full cold out of the center console.
The rotary temp setting switch has no effect on any operation of the heater. I have no control except fan speed and outlet settings.

Thank You for a response.
Don Umble

[Gilly]

What do you do to get heat out of it?
Gilly

Thank You for your response.

I get heat out by pressing the * or EC button and any of the arrow buttons. I seem to get heat from the right places in respect to which button I push. I get mixed air from the middle grill, so I normally close it, until it gets too hot, then I open it and reduce the fan speed and it stays fairly nice in the car. I was told by the dealer that sold me the car that the original owner, rather than have the AC controller fixed, had a repair person in some way rearrange the connectors on the back of the controller so that the button above the * button would turn on the air conditioner.
It works this way but there is no control.

I am a computer controls engineer and would like to pull the controller out and replace it with my own design using a microprocessor but I can't seem to find and real good wiring diagram for the controller input and output lines. I would leave the panel the same because I like the original appearance.

Thank You,
Don Umble
dumble@mcselph.com