Diesel Data: Automotive Repair
Home >> Buick >> 1985 >> Century V6-260 4.3L DSL >> Repair and Diagnosis >> Engine, Cooling and Exhaust >> Cooling System >> Radiator Cooling Fan >> Radiator Cooling Fan Motor >> Description and Operation

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.




V6-262 DIESEL VIN T
Two types of cooling fans are used: a single speed or a two speed cooling fan. The two speed cooling fan is controlled by a cooling fan relay that has two coils and two independent sets of contacts. During low speed operation, either low speed switch in cooling fan switch closes to ground or low speed switch in A/C high pressure switch closes to ground. The low speed coil of cooling fan relay is energized, causing contacts to apply battery voltage to resistor in two speed fan so fan runs at low speed. During high speed operation, either high speed cooling fan switch or high speed A/C high pressure switch closes. Circuit is then completed through high speed coil of cooling fan relay, causing battery voltage to be applied directly to cooling fan so it runs at high speed. The single speed cooling fan uses same relay and switch circuits without a resistor. It runs only at high speed controlled by low speed relay contacts (black/red wire), while high speed relay contacts (black/pink wire) are unused.




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.''




BUICK CENTURY V6-262 DIESEL VIN T
Fan Runs At Both Speeds When Jumped; Does Not Run In Normal Use
1. Disconnect connector from cooling fan relay. With ignition in RUN, measure voltage to ground at connector. Battery voltage should be available at terminal C (brown/white wire) and terminal G (red wire).
2. If any terminal does not have battery voltage, check circuit supplying terminal. If voltages are correct, proceed to step 3.
3. Re-connect connector to cooling fan relay. Disconnect connector from cooling fan switch and connect fused jumper from connector to ground.
4. With ignition switch in RUN, check that cooling fan runs at low speed when grounding dark green/white wire. Check that fan runs at high speed when grounding Lt. green/black wire.
5. If an does not run at one speed or both, check wires to fan motor and to cooling fan switch from relay. If wiring is OK, install new cooling fan relay.
6. With connector still disconnected from cooling fan switch, start engine. Turn A/C mode selector switch to NORM, and blower to HI, and leave vehicle doors open. Cooling fan should run at low speed, then at high speed. If not, install new A/C high pressure switch.
7. Re-connect connector to cooling fan switch and disconnect connector from A/C high pressure switch.
8. Turn A/C mode selector to OFF. Run engine at fast idle. Cooling fan should run at low speed and then at high speed, before temperature indicator comes on. Install new cooling fan switch if fan does not run at both speeds. If engine temperature is high enough that cooling fan is running at high speed, turn engine off. The cooling fan will switch to low speed as engine cools down.



Diesel-Data.com