This circuit for cars with fans was found in Silicon Chips documentation from the 90s. It is used to activate the fan when the radiator water temperature rises.
This circuit turns off after a time given by capacitor C1. This component can have from 1 to 1,000...
This interesting multi-channel circuit was found in the August 1988 issue of Radio Electronics magazine....
This circuit is from a 1974 publication, but it can be easily assembled using more modern...