Look at BUY PARTS on the top of this web site.
Look under "Vacuum Element"
They don't have them listed under heating.
I won't try to rebuild one of these it takes 4 hands with screwdrivers in each hand to open one up. The plastic is very brittle and tend to break. If you go to all the trouble to take apart a dash do it right.

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2009 CLS550 55,000
2004 ML350 144,000
2004 X5 95,000
2002 X5 165,000
1996 320S 155,000 (sold)
1991 190E 192,000 (sold)
1989 300SE 160,00 (sold)
1984 300D 210,000 owned since 85, (sold)
1984 300SD 160,000 (sold)