1997 2.3, the hose labeled 4 is disconnected from vacuum source in my truck, and I have AC default to defrost vents.

It literally looks identical to the diagram. Just hanging off the reservoir, seems to have become brittle and broken loose from wherever it's supposed to go.

Unfortunately the diagram doesn't show the where the loose end connects to, just "vacuum source". I cannot find the location of the intended connection on the intake or the remaining loose end of the red vac line to repair the connection.

Any help would be appreciated. Thank you!

 

Welcome to the forum

#4 goes to "Vacuum source", this means it connects to the upper intake manifold, but can be on a "T" with another vacuum device.

Follow each vacuum hose from the upper intake to where it goes, obviously look for broken red hose, on a "T" or on its own at the upper intake

There is a vacuum hose diagram on the rad support, it can be hard to read but might be helpful

These can be repair with a rubber vacuum hose of the correct size, just needs to slide it on to broken section, should be "snug" fit, its Vacuum pressure so sucks connections together no clamps are needed
Cut a section of the broken line off, and take it into auto parts store to get a length of correct size of rubber vacuum hose, good to have on hand as these hard plastic lines do break as they get older


The Grey vacuum line, unlabelled in the drawing just above #4 line, goes to the heater hose bypass valve, just FYI