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 BUICK CENTURY & OLDSMOBILE CUTLASS CIERA
System Description
The cooling fan is controlled by a cooling fan relay whose coil is grounded by the cooling fan switch when coolant temperature exceeds 228 degrees F. The cooling fan relay is energized and its contacts close to supply battery voltage to cooling fan. The cooling fan delay relay operates cooling fan for short time after engine is turned off. A solid state timer removes ground from cooling fan delay relay coil to switch off cooling fan.
V6-181 VIN E
Three types of cooling fans are used with V6-183 VIN E engines:
a. Single speed.
b. Two speed (internal resistor).
c. Heavy Duty Two Speed (external resistor).
On vehicles with single speed fan, cooling fan relay coil is grounded through cooling fan switch, which closes when coolant temperature exceeds 228 degrees F. With relay coil grounded, cooling fan relay contacts close and battery voltage is applied to cooling fan causing it to run. On vehicles with 2 speed cooling fan, the fan is controlled by low speed and high speed cooling fan relays. A resistor is connected in series with the cooling fan for low speed operation. On vehicles less A/C, two separate cooling fan switches are combined in a single unit. During low speed operation low speed cooling fan relay coil is grounded through low speed contacts of cooling fan switch. On vehicles with A/C, low speed cooling fan relay coil is grounded through solid state relay and A/C mode selector. The circuit to ground is completed when A/C mode selector in MAX, NORM, or BI-LEVEL position. When vehicle speed exceeds 35 mph and torque converter clutch is energized, ECM breaks connection to ground causing fan to stop. When vehicle speed is above 35 mph, ECM applies a ground to low speed cooling fan relay to energize solid state relay coil. (Same ground is applied to torque converter clutch and assembly line communications link connector.) The solid state relay contacts open to interrupt current flow through a second relay coil, whose contacts open to switch off low speed fan operation. When coolant temperature is above 228 degrees F, cooling fan switch closes to energize high speed cooling fan relay whose contacts close to apply battery voltage directly to cooling fan causing it to run at high speed.
System Check
BUICK CENTURY
Less A/C
1. Run engine at fast idle for several minutes.
2. Cooling fan should turn on before coolant temperature indicator in instrument panel comes on.
With A/C
1. With engine at normal operating temperature, and running at curb idle, set A/C mode selector to NORM position. Cooling fan should turn on.
2. Set A/C mode selector to OFF. Run engine at fast idle for several minutes. Cooling fan should come on before coolant temperature indicator on instrument panel comes on.
Troubleshooting
BUICK CENTURY
If cooling fan relay has failed, replace it and check cooling fan switch for intermittent operation as flows:
1. Warm up engine until cooling fan turns on.
2. Disconnect connector from cooling fan switch.
3. Connect self-powered test lamp to switch and to ground. Test lamp should light steadily.
4. If test lamp flickers, replace cooling fan switch.
5. Perform test on both high and low speed switches, if equipped.
Cooling Fan Does Not Operate
1. Check applicable A/C or heater fuse. On V6-231 VIN 3, check ECM/ERLS fuse.
2. On all models, check for loose connections on fan and relays.
3. If OK, connect fused jumper wire from positive battery terminal to cooling fan black/red and/or pink/black wires.
4. If fan does not run, check that black wire is grounded and that fan mounting bolts are clean and tight. If fan is properly grounded and does not run, replace cooling fan.
5. If cooling fan runs in step 3, problem is in control switches or wiring:
a. On vehicles with 4-151 VIN R, V6-183 VIN E with A/C, V6-231 VIN 3, perform ECM diagnosis.
b. On vehicles with V6-183 VIN E less A/C, or V6-262 Diesel VIN T, refer to ``System Diagnosis.''