The reason for the non temp gauge on the dash pointing to noon from damaging levels of hot pot to damaging levels of cold is literally to prevent customers asking too many questions during warranty period. (as according to tech builtin). They don't think the average user can handle the truth (literally).

When the tstat fails open it will take longer to get up to temp and won't even reach temp when ambient is low.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)