For the life of me I cannot find what the high and low pressures should normally be for the Air Conditioning on a 2002 SL500. I want to add freon but don't want to blow the compressor. Any help?

I'd shoot for 35/250 ensuring that the fan runs at 250. If the fan doesnt run over 250 it can hit 400 and it will find a way out at that kind of pressure.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
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3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
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90 300CE 104.980
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PCS TCM2000, built 722.6
600W networked suction fan
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V8 rear subframe, Quaife ATB 3.06 diff

What is meant by fan running at 250? Do you (or anyone) know where the tech specs for A/C pressures would be? Thanks

Here is the pressure chart for R-134a.

http://acprocold.com/wp-content/uploads/2011/11/Temp-pressure-chart-33776F1.jpg

I will caution you that this is not something you should be doing if you don't understand how automotive AC systems work. This might be better something letter the professionals handle.