How to clean the instrument gauge plexiglass??
 

I tried cleaning it with water and a special microfiber cloth. Helped a little but there is some kind of grime on the inside of the instrument guage cluster that won't come off......would windex work?

Seems to me I used Simple Green to clean the clear plastic and followed that up with either 303 Aerospace Protectant or Maguire's plastic polish. The hard part was getting the plastic static-free so dust wasn't attracted to the inside surface when I put the cluster back together.

I removed the cluster in my '83 300CD, took out the gauges and wiped the film off the inside with a microfiber cloth. I used a paint stirrer stick to get into the corners. I didn't want to put anything in the housing that would evaporate or create problems. It wasn't perfect but it improved it.

I also cleaned the film off the bulbs and wiped down the prisms to transfer light better.

I think the plain microfiber is less likely to scratch than paper towels.

I use a mix of ammonia and water. I take out the gauge guts and wash the outside first, then with the damp rag I wash on the inside, let air dry for a couple min and wala. Clean Cluster case

On helicopters in the Army we used something which had ' fiberglass cleaner and restorer ' in the name...
There is clear and there is ' optically clear ' ...
probably not hurt much to not find the latter... but lighted displays might produce scatter like having a cataract does to night vision.
I wonder if these new $6 polishing kits for making front light plastic covers clear again would work well ....

after I posted this, I located the following web site. They recommend a product called "Novus"....I checked it out and they have Novus #1, #2 and #3 for plastics and acrylics... found it on amazon and a few other web sites for under $20. it has to be less expensive than purchasing a new instrument panel plexiglass.....

mine has light scratches which I would like to remove. It will be interesting to see if Novus works.....I'll post back with results.

http://www.rplastics.com/plexcare.html

That is a good reference page....

I bought the Novus Plastic cleaner kit and it worked very well on the instrument gauge plexiglass. Mine looked like it had 'water spots' from being sprayed with hard water all over it. Of course, that wasn't the real problem, but it looked exactly like that. I used the Novus fine scratch remover followed up by the Novus plastic cleaner. It cleaned at least 85% of the gunk and the cluster set is much easier to see now, both in the daylight and at night.

As many aircraft owners have learned the hard way, ammonia (and ammonia-containing glass cleaners) are not well-suited for cleaning plastic. Repeated use is known to cause hazing.

Excellent choice.

Brillianize

http://shop.brillianize.com/all-products-call.aspx

Available at plexiglass suppliers.