To air condition my car, I used to set the climate control to 75, fan to auto, forget it, and stay comfortable during the summer. Now 75 either freezes me out or is too hot. I often have to move the selector to 80 or 70 to stay comfortable. The temperature is still regulated, I'm comfortable at the new setting, but the set point is all over the place each time. Is this a precursor to a serious problem?

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95 E320 Cabriolet, 169K