It will pick the resirc mode based on outside / inside temp. If they are different enough it keeps the resirc going. The switch will take it to 100% for 20 min no matter what mode it was in before, then 80% after that.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.