Fiber optics

I just bought a 1970 and most of the fiber optics work well. Two are a bit dim and the license plate optic does not work. Any quick fixes-a quick shot of compressed air, for example? I do not intend to re-do the optics (its not worth it to me) but easy tips to improve them would be good if there are any.
Thanks
Mickey

Compressed air won't work.
Try cleaning the ends at the bulbs, next clean under the console, sounds like it may be just dirt or overspray from a repaint.