38-41 is about as low as you'll ever see it go. There's a thermistor next to the evaporator coil that will kick off the compressor at 3-5˚C (37-42˚F) to keep it from growing ice. Once my SD has pulled the cabin down, it stays 42-44˚ on medium fans speeds and below.

The earlier cars will NOT work that well once converted since they had the old-school single-circuit fat-tube style condensers and woeful Delco R4 or mediocre Harrison A6 compressor. The updated '86-91 cars will though due to the upgraded condenser design and Denso compressor. The '88-91 cars got the dual-fan auxiliary fan setup (vs single 16" fan for '86-88, or single 12" for '81-85) that really helps at idle speeds and city traffic too.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]