If you have a healthy clutched fan, it's going to do most of the heavy lifting for the A/C system anyway. The electric fan is there for assistance on hot days when more airflow is needed.

The reason your system has a pressure switch to control the fan is because you actually DO need head pressure for the A/C system to work properly. If you have the fan blasting away all the time, you have operating conditions (wet, cool days, early in the mornings, etc) where the head pressure drops to the point that the A/C just doesn't really do any work. Even modern cars use pressure switches, listen next time you hear the compressor kick on, there's a delay before the fan kicks in. That's the pressure switch doing its thing.

Also make sure you upgrade your alternator if you're running the fan on high speed. The 70A in the cars that fan was designed for won't keep up at idle if you're running the A/C. You need 90A+ unless you just hate your battery.

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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]