So I have labored to rehab my AC. all dash pods have new diaphragms, new compressor, new dryer, new expansion valve, all cleaned as described in Dieselgiant's tutorial and foam tube for interior temp sensor repaired.

So I have cold A/C!

but...... the fan only stays on highest settings or lowest, no in between. I set the fan to auto, roll back the temp all the way to the shy of going into heat and the fan still blows on second to highest speed, and still full cold. The only way to lower from high sped fan is to select low fan button. Conversely when I use heat and slowly turn the temp setting toward a colder setting the fan still blows at or near full speed, but the temp of the air cools off.

I have verified the temp sensor in dash is drawing air in. I have removed and cleaned all internals on temp wheel. What should I look at now?

PS 1983 300D turbo

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1972 280SE 4.5