My center vents only work on economy, and close when the AC is on. I pulled a valve from the yard and might try that before I bypass anything, but I need to know which of the 6 valves controls the center vents. I tried pulling the lines off of the bottom 3 valves one at a time to see if that would close the vents while in economy mode, but they stayed open. removing the top 3 will take a little more effort so I just wanted to check here before I proceed. BTW, the CCU was recently rebuilt. Thanks

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'81 300SD