Help with Heat/Defrost/AC Rotary Switch

[spat61]

I have a 2002 chassis Land Yacht (Gas) 30' . The Climate Control has a hissing noise. I unscrewed the panel and quickly noted silicone all over the back of the unit. It was very difficult removing the silicone but it did reveal the cause of the hissing noise and the reason for the silicone. The white lead-in wire was being held in the port with the silicone but it broke loose over time. I temorarily forced a piece of tapered plastic in the port to stop the hissing (I suppose it is vacuum). Can anyone tell me if the white wire has important significance, or can I leave it unplugged with the stopper in the port just to stop the hissing.

Can someone explain the principle of how the heater/air/defroster rotary switch works.

Buying a used MH is a challenge.

Thank you.
Steve

[overlander63]

The selector uses vacuum to operate blend doors and control valves by taking regulated manifold vacuum from the engine and sending it to a combination determined by the position of the selector lever.
If the white vacuum hose has vacuum all the time the engine is running, it is the main feed for the selector, and it must be plugged in so the various doors and valve will operate. If it has no vacuum unless the selector is in a specific position, it can be blocked off, and everything but that one item will work, up to a point. Bear in mind some settings of the selector require use of more than one door, and leaving one out of the system will hinder the effectiveness of the system.