hose to dual heat control valve hose arrangement
 

frizzing climate force me to find why the heating is not working, i found that in the dual heat control valve ,there is not a hot water hose connected, i want to know the hose arrangement: where is to be connected from? see pictures,
my car is a 1998 slk230

The first and last pictures here:

https://www.benzworld.org/threads/slk230-heater-valve-duovalve-electrical-issue.1595600/

might help. Neither is ideal. This person was having a problem with the electrical side. It appears the hose goes out and toward the front of the engine compartment. Hopefully someone can give you a more specific answer. Hopefully they didn't do that because of a heater core problem.

Looks like your hose has been bypassed.