For 1990-2009 cars

#### Primary Cooling Fan

The cooling fan switches (7 and 6) and the A/C compressor relay (instead of the ECM) control the relays which power the primary fan (5) and two secondary fans. The primary fan is a "puller" type; the secondary fans are "pusher" type.

The following table explains the temperatures at which the engine cooling fans are energized or de-energized:

#### Engine Cooling Fan Operation Parameters

Temperature | Description
--- | ---
Energized
100°C (212°F) | The primary fan is energized at low speed using a resistor; the secondary fans are energized in a series (half speed).
105°C (221°F) | The primary fan is still energized at low speed; the secondary fans are switched to full speed.
110°C (230°F) | The primary and secondary fans are at full speed.
De-energized
105°C (221°F) | The primary fan is switched to low speed; the secondary fans are still at full speed.
100°C (212°F) | The secondary fans are switched to a series (half speed); the primary fan is still at low speed.
95°C (203°F) | All fans are turned off.

The secondary fans are energized in a series (half speed) during A/C operation. This could be stepped up to full speed, or the primary fan could be energized as well, depending on the coolant temperature.