If the aspirator isn't working, it won't be pulling air past the cabin temp sensor and could cause some unexpected behavior.

Cool but not cold could be refrigerant charge, or more likely the monovalve leaking by. Go lay eyes on the fat refrigerant line in front of the brake booster. If the metal part is sweaty and cold to the touch when the A/C is running, it's likely to be the monovalve or even could be the pushbutton unit. If the monovalve loses voltage, it will open and pass hot water through the heater core. There is no blend door, so it will be heater vs. A/C. Heater will win.

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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]