hi. i have a 1983 300sd that needs a new monovalve. when i look for this part there are two to chose from- one for chasisses with a heated windshield and ones without. how do i know which one i need?? how do i find out if i belong to chassises with number -019189 or 019190-?

http://mercedes.thebenzbin.com/?year=1983&make=MB&imageField22222.x=25&imageField22222.y=19

thanks!

nick