2001 E450 SD Vacuum check valve??
Hello...I have a 2001 Ford V10 E450 running my class C and just this weekend we were driving and notice the fan for AC or Heat or vent will go from dash air to defrost when the motor is under stress l...
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The checkvalve is a one way valve, be sure you instaled it in the right direction. Otherwise there must be a vacum leak. The red plastic tube goes from the manifold connects to the black rubber hose, runs through the fender comes out under the dash passenger side, goes to the vacumn motors on top of dash,and to the dash slector switch. In the middel on top the dash is axcess panel to the vacumn motors. Check everyware you can for leaks. Good luck.
