Vent control not working?

Hi,

Are you able to change between the defroster and floor vents? I ask because the air flow direction is controlled by what is called a function selector switch which is the center round knob on the dash.

That knob controls the air flow by diverting engine vacuum to the requested vacuum switch mounted on a plastic door. It is part of the HVAC unit under the vehicle.

So, not to confuse you, I suspect we lost engine vacuum to the center control knob. See pic below. In the picture, number 17 is the control knob on the dash. Numbers 1, 3, and 5 are the different doors that move. I highlighted the vacuum motor and circled the doors. Based on the doors positioning determines the direction of air flow.

I poorly wrote EGN and circled it. That is the engine and shows the vacuum supply hose.

First, start the engine. Listen closely under the dash to see if you hear a hissing sound when changing the air flow directions. If you do, try to locate it.

If there is no noise, then we need to remove the vacuum connector on the rear of the control knob and see if there is a vacuum supply from the engine.

Let me know if this helps or if you have questions.

Joe

See pics below. Note: The last pic is of the control knob. It is the rear where the vacuum harness would attach. Check there for leaks as well.

Hi,

That sounds like we have no vacuum present to operate the vacuum motors. Are you able to check under the dash to see if you can hear a leak with the engine running?

Let me know.

Joe