The subject invention detects the presence of an ozone reducing coating on an automotive radiator of the type having spaced fins presenting electromagnetic surface properties different than the electromagnetic surface properties of the coating. In accordance with the subject invention light rays are emitted or reflected off the coating on the fins to a detector and a comparator compares these light rays to a predetermined benchmark to provide a signal in response to the detected light rays crossing the benchmark. In a species, a second detector is employed to detect rays from an un-coated section to establish the benchmark.