Dehumidified Defrost needed?

Now that’s a good idea!
What about one of these? Or two of these with a switched vacuum solenoid? Would open one/close the other…

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I saw those while looking. My only hesitation or concern was that you'd need two of them, as opposed to the ones built into an existing Y-pipe. On the flip side, the price seems right.

I wondered aloud (to the dog--I'm not crazy) how well that vacuum diaphragm would withstand exhaust heat. She seemed uninterested. Coolant-level temperatures shouldn't be a concern a'tall, though.