Whenever I have a load on the engine my vents seem to change ease off the gas the vents will change. it will go from the vent to the defrost. I think I am loosing vacuum. would I be loosing any power or performance if a vacuum line is off? Can someone let me know. really annoying problem. 2001 4x4 5.9
thanks

 

same problem here,when i give it gas it goes from vent to defrost,let off the gas it goes back to the vent,really no lack of power loss though.[sm=confused06.gif]

 

Sounds like a bad check valve somewhere. Checks all the lines, and the check valves as well. Vacuum lines can be deceiving. You have to inspeact closely.


Good luck.

 

I have a similar problem, except I won't even be on the gas and it will change...

 

On a 01 I belive there are two check valves. One at the intake and another where the vacuum line tees off to the hvac control. These prevent the motor from robbing the vacuum form the hvac actuators.They are pretty cheap. $5 to $10.

Jer

 

does anyone have a link to a picture of the way it is layed out. i have a link here for the older models but was wondering if anyone had a up to date picture. here is the link
Click here: TSB 24-01-96 Rev. A

 

I hope this works. They are #2

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had same problem with my 97, loses vacuum to the blend doors which causes them to close and send air through the defrost vents. Had a bad check valve on the brake booster, changed it and it seems fine. havnt had problem since