Strange scratching sound coming from dash while using cruise control

[Bucky Marino]

Strange thing has been happinging.



While driving in cruise control at around 50 mph, the dash board makes a strange scratching noise when the truck goes up a hill, or does anything that strains it a little. It doesn't do this at higher/lower speeds.

 

[swshawaii]

Check this TSB link. Thank Steve M if it works.

 

[swshawaii]

Here's another:

 

[Mike S 3]

could be vacuum related, a bad check valve between the Vac reservoir and the intake plenum. When going up a hill the engine is under a lot of load using cruise, and the engine vacuum is very low or zero. So without vacuum your blend door is moving.



Try to change your climate controls from floor, dash, vent, adjust the temp from full cold to hot, etc and see if the scratching noise happens then too... If so, it's a bad check valve.