Refinish AC undressed fibreglass cover

[SS427]

If it is not badly sunbaked I have had really good luck using plastic media or glass media at a low pressure. As Roger says, if it is really bad respraying the resin will really help. Here are some before and after shots of a case that was not horribly bad to begin with. I light media blasting followed by a satin clear really spruced it up. Fiberglass heater boxes are the same and are usually in much better condition to begin with.
Rick

[ORIGLS6]

Satin Clear is a good choice. I also had good results using oil based polyurethane a few years ago. (The spare tire carrier on a Corvette.)

I hit the worst areas with 0000 steel wool, then rubbed the matte/satin polyurethane on with a cloth. It soaked in quite a bit in some areas but I went back over those until they were saturated.

Gotta be careful with the steel wool. Those fibers can poke through the wool and put some nasty holes in your fingers!