2nd Gen Non-Engine/Transmission 97 12v - Vents stuck on defrost only

[GrantP]

After doing some work under the hood, I noticed the air is only blowing out of the defrost ducts, regardless of the position of the vent control knob. There are two plastic vacuum tubes that are connected at the firewall, one appears to go to the cruise control underneath the drivers side battery, the other is laying loose. Obviously I accidentally yanked it out, but after staring under the hood for 30 minutes and flipping through the factory manual, I can't figure out where/what to connect it to? Thanks for any help.

 

[Batphreak]

The line not going to the cruise on mine goes over the engine and connects to the HVAC system on the passenger side. Don't know what else to say, Cruise, HVAC, and Center-Axle-Disconnect are about the only things running on vacuum with these trucks.

 

[Joe G.]

The heater/AC vents are vacuum controlled. Check on the passenger side where the heater pipes go through the firewall. There is a vacuum pipe there too. You may have pulled it out of the connector or it may have melted shut or in two pieces. When mine did that it was inside the push together vacuum connector so make sure you pull it apart and check that if you don't see any other bad place.

 

[DieselDoghouse]

what everybody else is saying. On my truck there is a manifold array of vacuum lines that arrange as follows from drivers to passenger:



Vacuum supply from pump

vacuum to cruise control

vacuum to transfer case for axle disconnect

line across firewall to/near heater hoses running inside for HVAC motors.



also, make sure that any caps on blind ports are in place. Losing vacuum through an open line is as good as a disconnected hose.

 

[GrantP]

Thanks to everyone for the responses. The vacuum line near the heater hoses was still connected. The vacuum tube that goes from the vacuum pump to the junction on the firewall was disconnected at the pump. The power steering hose was laying on top of the connector at the pump and I never saw it. Problem solved.