I have a grinding noise on my F150 Mark LT pickup
Ford has issued a service bulletin to address a Grinding noise F150 Mark LT pickup problem on these vehicles. The noise appears to come from under the dash and happens when you switch modes from heat to defrost or vent. The noise is caused by the mode door motor cam plate and the cam.
To fix the problem, turn the HVAC control to PANEL mode. Leave the mode door connected to the cam plate and remove the four bolts holding the cam plate to the upper plenum. Then remove the motor and cam plate together, as an assembly. Now you can remove the cam plate and the cam. Turn the cam over and wipe awap all the grease. Then apply a special teflon grease (Ford part #XG-8) in the same areas you just cleaned. Put all the components back and test the HVAC by switching between the PANEL and DEFROST modes several times.
© 2012 Rick Muscoplat