How do modern cars regulate temperature so well?

Dana67Dart said

PROPERLY sized electric fans and controllers will make a difference as well

All that being said. There is a hill on the interstate near my house, long and steep. When going up in the winter you can feel the heater air get hotter as you crest the top (Mini van).

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True on the fans.... I too, can feel the difference on our mustang by grabbing the radiator hose between a cold Fall day or a Hot Summer day, yet the gage reads the same...... I think if the temp stays in "normal" op range, the gage stays still. Again, I could be wrong....