While hunting for another component under the dash on the passenger side of my 1985 300D I noticed a rotted piece of foam hose which seemed to be joining two plastic pipes each about 1 inch in diameter. One pipe went to the inside temperature sensor grill at center of dash. The other pipe went to the blower assembly behind the kick panel. What is the purpose of these pipes? Is there a reason foam hose was used to join them? I replaced the rotted foam with a 6 inch length of rubber hose but don't know what it is doing or should be doing.