I have a 97 ram 1500 3.9L V6. It has a vacuum leak that defaults the cabin air to defrost. I am also getting an engine light code for the idle speed being too low. The diagram on the engine compartment shows the two lines that come off the passenger side of the manifold run to the climate control and the vehicle speed control. The small line that tees off the top of the line is broken off, but I can't find the line that was attached. I think it goes to the vehicle speed control, but I don't know where it is located. I checked the idle air control and the vehicle speed sensor, but I don't see a vacuum line at either location. Please help.

 

Idle air control is electro-mechanical, No vacuum required. Same for the VSS.

A broken vacuum line will give you a leak, and so your vents won't switch. Should be a vacuum line diagram sticker under the hood somewhere, if not, should be one if the FSM.

Low idle is going to be a separate issue. If you still have low idle, even with a vacuum leak.... something is definitely awry.

Welcome to DF!

 

It's under the battery on my 95. On my truck it superceded to a different style and required a $50 wire harness adapter..

 

The line T's and goes up over the front of the engine to the speed control servo. The other part goes to the firewall on the passenger side. One line goes to the heater control, another to the vacuum reservoir in the cowl. If you have 4x4 a line T's off and goes to the transfer case also. A picture would help.