Century L4-151 2.5L VIN R TBI (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 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.
4-151 VIN R
The cooling fan is controlled by the following:
1.
Coolant temperature fan switch.
2.
ECM and A/C mode selector switch.
3.
ECM and A/C high pressure switch.
These switch combinations complete circuit to ground through cooling fan relay coil. With coil energized and relay contacts closed, battery voltage is
applied to cooling fan.
On vehicles equipped with A/C, cooling fan also runs when compressor is on. With A/C mode selector is in MAX, NORM, or BI-LEVEL position, a
path to ground exists through mode selector switch and ECM.
A suppression resistor is connected across cooling fan relay coil to absorb voltage spikes. An A/C high pressure switch is included in A/C relay
grounding circuit to ensure grounding of cooling fan relay coil and cooling fan operation when mode selector is in DEF position and ambient
temperature is above 32 degrees F.
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.''
