Can't say it enough...
...even if you don't have cracks, you will eventually. Take the panels off and do the fix. It won't even take a whole day, just a few hours and you never have to worry about it again.
For the guys and gals with the cracks all the way through to the insert...the fix wont work. Only solution is to get another door panel and then reinforce that one so it won't crack.
My do it yourself is post 159 here:
Cracked interior door panel...:( *DON'T QUOTE PICS!
Good luck
Oh and its not the sun. Well not directly, anyway. Its the temperature rather than the UV. The variations in temp cause the plastic to expand and contract, but the panel is reinforced along the window guide with a steel insert that doesn't allow it to do so freely causing the crack at a weak point.
__________________
2002 Trans Am Collector Edition WS6 ASC# 619
Coupe
| Collector Yellow on Ebony Leather
| A4
| TCS
| #126 of 510 T-Top w/A4 made
CETA 619 "The Falcon" CE Owner Site:
www.collectorfbody.com 1999 30th Anniversary Bandit Edition Trans Am WS.7-SOLD
Special Bandit Edition Anniversary Package (WS.7) Black/Gold on Pewter Leather
| M6
| CF Int. Trim
The Bandit Pics 2009 Aggressive Solstice 2.4L-Daily Driver
"Chief" pics 
