I'm checking the operation of all my vac pods. Most work. Very confused about the proper operation of the center vent pod.

My understanding is that this is a single element pod, meaning that vac is applied to move it in one direction, and spring tension moves it in the other. But which is which?

When I manually open the center vent, then switch to 'heat' the system gives a very weak, half-hearted effort to close the center vents. With the vents closed, selecting 'AC' does nothing, and the vents just stay closed.

Should I be looking for vacuum to open the vents in AC mode or close the vents in heat mode, and do I have the proper general understanding of the operation of the center vent vac pod?

Thanks,

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Bob
'82 300D Petrol B-G Metallic

I am no mechanic but I just messed around with mine yesterday and if I had to make an educated guess watching them operate. I would say the spring keeps them in the closed position and the vac is used to open. also somthing to consider like on my car I noticed the defrost pod seemed to work fine however it still didn't close all the way. can appear to operate fine but still have some probs. Used a zip tie as a temporary fix. check the thread on weak center vents.....

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83 TD wagon "Madge" PO's given name. 410k (150k engine)