I've had the new Klimakit valve in my hands to install on the W126 300SD. It looks to be very well designed and appears to be a drop in replacement. I'm waiting on a replacement since the Postal Service used it for training purposes. The electrical connector was broken off. Klimakit is replacing it.

On my '76 450SEL, I had a ball valve for heat control. Shut in summer, cracked in spring and fall and mostly open in winter worked just fine. Temp was controlled by switching fan speed and which vents the air came out.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120