David,

My '91 190E 2.6 did the same thing, exactly. Cold air from the center vent(s) and warm or hot air from the side vents during a long hill climb.

Going on level ground was no problem but making a protracted hill climb, the side vents would kick out hot air. Sounds like your car does the same thing.

I was told it's a vacuum leak and/or bad element (switch) in the center control console.

Never did fix it, just sold it so don't know what it took to fix it.

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Regards . . . . JimF
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'94 S500 Cpe

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