Fiero L4-151 2.5L (1985)
Radiator Cooling Fan Motor: Description and Operation
On models equipped with electric engine cooling fans, the battery ground cable should be disconnected whenever underhood service is performed.
1985---87 PONTIAC FIERO
SYSTEM DESCRIPTION
Single Speed Fan
A cooling fan relay controls operation of the cooling fan. Voltage is always available to relay contacts through fusible link A (located at RH front of
engine compartment, at battery junction block). With ignition switch in RUN position, voltage is available through C-H fuse on 1985 models or E fuse
on 1986 models, to relay coil. At coolant temperatures above 235 degrees F, coolant temperature switch closes. Current flows through the fuse, the
cooling fan relay coil, then the closed coolant temperature switch to ground, causing relay contacts to close. Current then flows through fusible link A,
through closed relay contacts, through cooling fan to ground, causing cooling fan to run. On vehicles equipped with A/C, cooling fan relay is also
operated by A/C high pressure switch when closed, or by A/C mode selector when in MAX, NORM, or BI-LEVEL positions.
Two Speed Fan
Voltage is always available through fusible link A (located at RH front of engine compartment, at battery junction block), to low and high speed
contacts of cooling fan relay. With ignition switch in RUN position, voltage is available through the fuse to low and high speed coils of cooling fan relay.
With A/C mode selector in MAX, NORM, or BI-LEVEL position and with either A/C high pressure switch closed or low temperature side of coolant
temperature switch closed, current flows through the fuse, through low speed relay coil to ground. The low speed contacts then close. Current then
flows through fusible link A, through low speed relay contact to terminal C of cooling fan, through an internal resistor, through fan motor and to ground.
Cooling fan then operates at low speed. With high temperature side of coolant temperature switch closed, current flows through the fuse and high
speed relay coil to ground, causing high speed contacts of cooling fan relay to close. Current then flows through fusible link A and the high speed
cooling fan contacts to terminal B of cooling fan. Current then flows directly through fan motor to ground, causing cooling fan to operate at high speed.
TROUBLESHOOTING
Cooling Fan Does Not Run
1.
Check C-H on 1985 models or E fuse on 1986---87 models.
2.
Check fusible link A.
3.
On vehicles with single speed fan, connect jumper wire from Low Speed cooling fan relay coil (dark green/white wire) to ground. Cooling fan
should run.
4.
Vehicles with two speed fan:
a. Connect jumper wire from low speed cooling fan relay coil (dark green/white wire) to ground. Cooling fan should run at low speed.
b. Connect jumper wire from high speed cooling fan relay coil (Lt. green/white wire) to ground. Cooling fan should run at high speed.
Cooling Fan Runs Constantly With Ignition In RUN
1.
Check that coolant temperature switch contacts are open with engine cold.
2.
Check that cooling fan relay contacts are open with ignition off.
3.
On 1986---87 models, ensure A/C coolant fan relay contacts are open with ignition switch in RUN and A/C ``Off.''