Mercedes SL Outside Temperature Sensor Fault

That's a peculiar situation. Similar symptoms plagued a 2014 BMW 3 Series I maintained some time ago. The root cause resided in a faulty temperature sensor. Have you performed any sensor diagnostics, perhaps checked the vehicle temperature gauge readings?

Diagnostic checks have been performed and are inconclusive. Sensor malfunction suspected. Considering a temperature sensor replacement and sensor calibration. Are those steps the correct process in your experience?

Given your description and diagnostic outcomes, those steps are reasonable. However, are you equipped for sensor calibration post-replacement? It is an essential, but frequently overlooked, step. I would suggest engaging a workshop.

Thank you for the advice. I proceeded with temperature sensor replacement at a qualified workshop and subsequent sensor calibration. The issues are resolved. Total repair cost 95€.