There are a few steps you can take to determine if an old 35mm film camera is working properly:
1. Check the battery: Make sure the battery is fresh and properly installed. If the battery is dead or not installed correctly, the camera may not function properly.
2. Check the film: If the camera has film already loaded, make sure it is properly advanced to the first frame. If the camera is empty, load a fresh roll of film and advance it to the first frame.
3. Check the lens: Make sure the lens is clean and free of any dirt or debris. If the lens has a filter, make sure it is properly screwed on.
4. Check the viewfinder: Look through the viewfinder to make sure it is clean and clear. If it is dirty, use a soft, dry cloth to gently clean it.
5. Check the settings: Make sure the camera is set to the correct ISO (film speed) and that the exposure compensation, if available, is set to the correct value.
6. Test the camera: Take a few test shots to make sure the camera is functioning properly. Check the results on the film to make sure the exposures are correct.
If the camera passes all of these tests, it is likely in good working condition. However, it is always a good idea to have an old camera checked by a professional before using it extensively. This can help ensure that it is in good working order and that there are no hidden issues that could cause problems later on.