I have one that is over 10 years old any way to clean them or just get a new one this one is still charging looks really bad

If it still charges your battery fully then keep using it. Don't clean it. If it's not fully charging your battery then throw it away and buy another unit.

Look at some utube videos on cleaning car headlights.

Works pretty well on smooth ones but not so much on the bumpy ones.

I hooked up a motor on my son in laws barrel last weekend. Everything was new except the solar panel. I checked it was a meter at home (without installing it) and it worked great. I get to the lease and hook everything up and the digital timer is acting weird and saying the new battery was dead. I had charged several brand new ones. I tried a different battery with the same results. I disconnected the sole panel and everything worked great. Not sure why that happened but long story short he will buy a new solar panel. Nothing worse then finding out opening morning your stuff hasn’t been working because of a weak link.

For the same reason I’ll never use a plastic lid ever. Something chewed a hole in one years ago and basically I ended up with a barrel full of fermented corn on opening morning. Ha

I would say get a new one that you know works.