Did they move the aspirator in '87? In my '86 it's immediately to the right of the glovebox. There is a duct in the way to the right hand vent, but you can work around it. It just unclips and rolls up and out.

Focus on the A/C system health first. By putting the temp wheel on the blue dot, you're effectively bypassing the temp sensor. The system should try to run as cold as it possibly can. If you start noticing the compressor cycling, you could have a problem with the evaporator temperature sensor, but you'll never know until you observe the system in operation.

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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]