87 Dakota heater controls

[francis higgins]

I have a 1987 Dakota with a 3.9 V-6. The heater control panel is partially vacuum controlled. The vents keep going to the defrost and floor regardless of which location I select (panel, floor, defrost, etc.). Nothing has been messed with as far as vacuum lines behind the dash or under the hood. Is there a simple explanation for this. The truck has over 170,000 miles on original equipment. Thanks for the help.

[J-BODY]

Vents are in "default mode" which basically means that in case of failure you will have defrost. (for those in the cold country). Sounds like you have a vacuum leak or a control head prob. Find the vac source line under the hood and check it. If ok pull the control head and check vac at it. A service manual will have the vac diagram for this to test the vacuum actuator motors.