The W124 car had all the vacuum hoses messed up going into/out of the passenger cabin.

I can only think of 4 hoses going into/out of the cabin.

1) Vacuum shut off TO ignition switch ( brown )
2) Vacuum shut off FROM ignition switch to IP ( brown )
3) Vent into cabin ( black )
4) Climate control into cabin ( green )

There seem to be an extra one ( white ) laying around. Any idea what could it? Or it is just the mess up left over from PO.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.