Some 2005-08 Ford F-150 and 2006-08 Lincoln Mark LT pickup trucks may produce a grinding sound from the dash when switching modes at the HVAC control panel.
According to Ford, the noise is limited to vehicles built after Nov. 29, 2005, and is most likely due to contact between the mode door motor cam plate and the cam. Cleaning out the existing lubricant from the cam and re-lubricating it with a special grease, Part No. XG-8, should eliminate further trouble.
Start the fix by placing the HVAC controls in the panel mode. Leaving the mode door motor connected to the cam plate, remove the four bolts that attach the cam plate to the upper plenum. Now remove the motor and cam plate as an assembly from the vehicle.
Next, remove the cam plate, followed by the cam. Flip the cam over and wipe away the existing grease.
Using the illustration above, apply the new grease to the cam tracks and side channels in the areas shown. To complete the repair, put everything back together, start the engine and cycle the control panel from panel to defrost several times to allow the grease to distribute evenly in the cam.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].