Where is the rotary thermostat's sensing bulb located? ( the end of the sensing wire ) - it is placed inside the AC box. It is inserted where the original thermostat used to reside

It is much better to control temps by moving the blend door in the heat / AC system. - I think the flaps and the pods have been disabled and are no longer working

USV = US Version. I am noted this because the Euro Version has a different set of AC controls. I have another car, Euro Version, heater also taken off. The temperature is regulated by turning on and off the compressor. This car one works fine

How it has been hacked / changed from original version
1) thermostat replaced as shown in the figure
2) The flaps / pods no longer work
3) The heater components have been gutted out

IT IS NOT better to control temperature by using the flaps... in Hot and Humid climates and OLD systems often converted to the less efficient 134a one often NEEDS the recycling of the inside air to be maximized... just to drop out a reasonable amount of HUMIDITY.... some even find it advantageous to block off the fresh air flap to less than the usual 20% ( ? ) ratio.
Typically the sensing bulb end is in contact with the top of the evaporator inside the AC box...that is where its purpose.. to AVOID freezing temperatures inside the evaporator functions best... because once freezing temps occur.. then ambient air humidity starts FREEZING on the fins... quickly cutting off air flow completely through the AC...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html