I did not experience the climate control; id;e speed related problems that you had.

One way to sort of check the coolant sensor without removing the cross-over pipe is to start the engine cold, then pull on the accelerator cable to increase the idle speed to at lest 1,500 RPM while watching the rod on top of the engine. (The one connects to the accelerator cable) It SHOULD NOT move.

Repeat this process when the engine reaches operating temperatures. At that point when you increase the idle speed to above 1,500 RPM that rod should pull on its own. If that works it will indicate that the coolant sensor is likely working correctly. If not, it likely is your coolant sensor, or its associated wiring.

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'95 E300 Diesel, 264,000 Miles. [Sold it]