Methods, systems, and apparatus, including computer programs encoded on computer-storage media, for a device with improved ambient temperature detection. In some implementations, a device includes a housing that forms an interior space, and the housing includes an exterior surface, a pass-through region that defines a through-hole between the interior space to the exterior surface, and a recess at the exterior surface adjacent to the pass-through hole. The device includes a printed circuit board disposed within the interior space of the plastic housing. The device includes a flexible printed circuit substrate including a first end region that is connected to the printed circuit board that is disposed within the interior space of the housing, a second end region at an opposite end of the flexible printed circuit substrate than the first end region, that is disposed in the recess at the exterior surface of the housing, and a middle region that passes through the through-hole between the first end region and the second end region. The device includes a temperature sensor disposed at the second end region of the flexible printed circuit substrate in the recess at the exterior surface of the housing. The device includes a protective layer that is disposed on at least a portion of the exterior surface of the housing and that covers the recess and the through-hole.