Firebird V8-305 5.0L VIN E TBI (1989)
Radiator Cooling Fan Motor: Description and Operation
VIN 8
The coolant fan is controlled by the ECM. In the 6 cylinder, the coolant fan is also controlled by the redundant cooling fan switch. When the ECM
grounds circuit 335, the coolant fan relay is energized and battery voltage is applied to the coolant fan. If the ECM fails on the 6 cylinder engine, the
redundant coolant fan switch will ground the 335 circuit and energize the coolant fan relay. The ECM will ground the coolant fan relay when the coolant
temperature sensor indicates the coolant temperature is greater than 222°F or when A/C control head pressure is greater than 233 psi and vehicle speed is
less than 40 mph.
The auxiliary coolant fan, used on the 8 cylinder engines, is controlled by the fan pressure switch and the auxiliary coolant fan switch. If one of these
switches closes, the auxiliary coolant fan relay is turned on. When a switch is closed, terminal D11 of ECM connector C2 is grounded. This tells the
ECM that the auxiliary coolant fan should be on.
VIN E
The coolant fan is activated by the coolant fan switch. The switch closes when coolant temperature is over 238°F completing a path to ground through
the coolant fan relay windings. The relay contacts then close and voltage is applied to the coolant fan. When the coolant temperature drops to 214°F, the
switch opens and the coolant fan stops.
In A/C equipped vehicles, the A/C control head completes a path to ground for the coolant fan relay. Voltage is then applied to the coolant fan.
