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 BUICK SKYHAWK, OLDSMOBILE FIRENZA & PONTIAC SUNBIRD
SYSTEM DESCRIPTION
The cooling fan cools both engine coolant and A/C system refrigerant.
4-110 Turbo VIN J
The cooling fan can be switched on by either the cooling fan relay (located on front of dash, left of master cylinder) or the 5 minute turbo fan relay (located on LH front fender, forward of shock tower). Both relay contacts always have voltage available from fusible link C (located at starter). With ignition switch in RUN position, voltage is available from C-H fuse to cooling fan relay coil and to solid state control in 5 minute turbo fan relay. When engine coolant temperature exceeds 238 degrees F, cooling fan switch (located on RH front of engine, on coolant outlet) closes, signalling solid state control in 5 minute turbo fan relay to close contact which provides path for current to cooling fan. When ignition switch is turned off, contacts in 5 minute turbo fan relay close and set 5 minute timer, allowing cooling fan to run for 5 minutes.
4-110 VIN O
When coolant temperature exceeds 238 degrees, cooling fan switch (located on front RH side of engine, bottom of thermostat housing) provides ground for cooling fan relay (located on front of dash, left of master cylinder). The relay energizes and current flows from fusible link C to cooling fan.
When A/C mode selector lever is in MAX, NORM, or BI-LEVEL position, and vehicle speed is below 35 mph, ECM will provide path to ground for cooling fan relay so A/C refrigerant can be cooled. At speeds above 35 mph, ECM shuts off cooling fan.
At high refrigerant pressures, A/C high pressure fan switch (located on RH front of engine, near LH end of compressor) sends voltage to ECM, which then switches on fan.
SYSTEM CHECK
With A/C
1. When engine at normal operating temperature and idle speed, set A/C mode selector to NORM. Cooling fan should turn on.
2. Set mode selector off. Allow engine to run at fast idle for several minutes. Cooling fan should turn on before coolant temperature indicator in instrument panel comes on or before coolant temperature gauge reaches H.
3. On models with 4-110 Turbo VIN J engine, turn engine off when at normal operating temperature. Cooling fan should run for 5 minutes.
Less A/C
1. Run engine at fast idle for several minutes. Coolant fan should turn on before coolant temperature indicator in instrument panel comes on or before coolant temperature gauge reaches H.
2. On models with 4-110 Turbo VIN J engine, turn engine off when at normal operating temperature. Cooling fan should run for 5 minutes.
TROUBLESHOOTING
1. If cooling fan only comes on with A/C compressor and not for a hot engine, install new cooling fan switch.
2. Connect a fused jumper wire from positive terminal of battery to terminal B (black/red) on all Buick Skyhawk engines and on Oldsmobile Firenza and Pontiac Sunbird with 4-121 VIN P engine; to terminal B (red/white) on Pontiac Sunbird with 4-110 Turbo VIN J engine; to terminal A (red/white) on Oldsmobile Firenza and Pontiac Sunbird with 4-110 VIN O engine.
a. If fan runs, ECM diagnosis must be performed since circuit is controlled by ECM.
b. If fan does not run, check continuity to ground at terminal B on Oldsmobile Firenza and Pontiac Sunbird with 4-110 VIN O engine; terminal A on models exc. Oldsmobile Firenza and Pontiac Sunbird with 4-110 VIN O engine.
3. If a cooling fan relay has failed, test cooling fan switch for intermittent operation as follows:
a. Warm up engine until cooling fan comes on.
b. Remove connector from cooling fan switch.
c. Connect self-powered test lamp to switch and to ground. Test lamp should light steadily. If test lamp flickers, install new cooling fan switch.
d. Test both high speed and low speed switches if vehicle is so equipped.
COOLING FAN, REPLACE
1. Disconnect battery ground cable.
2. Disconnect wiring from fan motor and frame.
3. Remove fan assembly from radiator support.
4. Reverse procedure to install.