Heater/AC vent option knob produces knocking sound in back right corner. i.e. the knob rotates from vents in front to half front half floor to all floor to half floor half defrost to all defrost. the sound comes in at vent to floor option and further on. The problem only exists when the rear heater/ac power knob is turned to level 1, 2, or 3.

Anonymous provided their own fix. Good job but you may need to fix it again when Summer comes.

I fixed this problem. I removed the Vent Mode Actuator from under the dash on the drivers side, then I moved the vent shaft by hand. I noticed some of the plastic parts attached to the shaft didn't move when I rotated it, so I just rattled the parts around with my finger. (I think one of the plastic gears inside had jammed and the rattling unjammed it) In any case, the internal louvers are moving with the shaft now, and heat is coming out of the front vents as it should.

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Blend air door actuator may be bad.

Sounds like your heater coolant hose door flap is broken or loose. May want to check behind the heater controls, if your components are mechanically operated. If electronically, may need to perform more troubleshooting before replacing this component.

Try this calibration procedure and let us know if you have more questions:

1. Start the vehicle.
   
2. Wait 40 seconds for the HVAC control module to self-calibrate.
3. Verify that no DTCs have set as current DTCs.
4. Clear all DTCs.
5. Place the ignition switch to the OFF position.
6. With the Mode knob in the PANEL position, press and hold the AC button for 5 seconds.
7. Rotate the Mode knob fully counterclockwise.
8. Rotate the Mode knob fully clockwise.
9. Rotate the Mode knob fully counterclockwise.
10. Release the AC button.
11. Wait 40 seconds for the HVAC control module to self-calibrate.
12. Start the vehicle.
13. Verify that no DTCs have set as current DTCs.

Sounds like a bad actuator on the dampner. Look for things connected to the ducting, see if you can manually open and close the dampner.

Have you checked the Aux switch near the bottom of the center control console.
There should be a knob with: Aux, Off, 1, 2, 3. This is the switch for the rear AC blower.
If the driver wants to control the rear AC, use the 1, 2, 3 settings.
If you put it on Aux, Than the rear AC is controlled by the passenger in the back seat using the extra controls located on the Overhead DVD player. (The front AC must be on the rear to work)

Hope I was avle to help, glad you up and going.

make sure the control knob on the dash is on "RR". This lets the driver control all the vents in the back. The heat only comes out of the floor vents, if you have the knob on the blue dots that represents the air conditioning in which the cool air will come out of the vents up above in the back. There is also an area on the control knob on the dash where you can turn the knob to shut the heat and air conditioning off. If the knob is in this position then you can control everything with the knob up above the seat right behind the driver's seat.

I HAD THE SAME PROB WITH MINE I REPLACED THE HEATER CONTROL PANEL & IT FIXED IT

You have a vaccum leak on the mustang. Unsure of the Contour.. I believe it is the middle hose where the three fittings are (right in front of the driver seat in the engine compartment) Mustangs are notorious for vaccum leaks there