Worldwide, in the W124 series for example, Mercedes-Benz fitted three types of ventilation/AC systems:

1/ The standard heat-ventilation only unit, with rotary dials for air direction, air temperature (left and right), and fan speed. No A/C and no recirc buttoms. Hence no A/C system and compressor.

2/ The "less expesinve" manual A/C system, which mimics all the rotary dials from above plus three push buttoms: A/C compressor turn-off buttoms (marked as EC or economy), air recirculation and auto windshield defrost settings.

3/ The "more expensive" fully automatic A/C system, which is the push buttoms auto A/C system fitted as standard in the U.S.A.

Since I had system No. 2 on my 300TE and system No. 3 fitted to my E 320 T, I can say that the less expensive A/C system with the rotary dials and separate temperatures for left and right highly exceeds in convinience and reliability the auto A/C system.

This opinion applies to the W124 (and also the auto A/C fitted to the W126, which is basically the same).

My opinion changes on the auto A/C system fitted to W140 series, which was mostly fitted for the worldwide market(including the U.S.). This system is really superb and provides great flexibility. Reliable? Well, I hope it is!

One important thing: the W140 in some specific markets was fitted rotary dials (similar to those on system No. 1 on the W124) without A/C and with a NON-auto A/C system similar to system No. 2. My S 500 L owner's manual covers all three of them.

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A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]