I understand that the 4th gen fans are wired to run in series when they turn on, then when the temp threshold is met, they go to parallel. Any advantage to running this way instead of single full speed first, then both ? Any disadvantage besides another relay?

 

Afgun,

The advantages I can think of would be:

More even airflow across the entire radiator;

Slower fan speed at lower temperatures (somewhat of a poor-man's variable speed);

Softer fan motor starts providing less wear on the bearings, brushes, commutator, etcetera;

Lower power consumption (I=E/R);

Quieter operation.

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Later,
Vader
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If you want to beat the World, it might reach up and pull you down...
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