Century Estate Wagon L4-151 2.5L VIN R TBI (1987)
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.
1986---87 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 Cylinder Models
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 low pressure cut-off 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 operates 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.
TROUBLESHOOTING
4-151 VIN R
1.
Check applicable A/C or heater fuse using a suitable fuse tester.
2.
If coolant fan does not operate when engine is hot, but does operate when A/C is ``On,'' proceed as follows:
a. Remove connector from coolant fan switch, then ground dark green/white wire. If coolant fan operates, replace coolant fan switch. If coolant
fan does not operate, check dark green/white wire for open, then repair as necessary and proceed to step 3.
3.
If coolant fan does not operate at all, proceed as follows:
a. Disconnect coolant fan relay, then connect a suitable test lamp between terminals C and ground. If test lamp does not light, check
brown/white wire for open and repair as necessary. If test lamp lights, proceed to step b.
b. Move test lamp lead from terminal C to terminal E. If test lamp does not light, check red wire and fusible link C for open and repair as
necessary. If test lamp lights, proceed to step c.
c. Disconnect dark green white wire from coolant fan switch, then jumper terminal of this wire to ground. With ignition switch ``On,'' connect a
suitable test lamp between terminals C and B of coolant fan relay. If test lamp lights, proceed to step d. If test lamp does not light, check dark
green/white wire for open and repair as necessary.
d. Disconnect coolant fan relay, then connect a fused jumper between terminals E and A of connector. If test lamp does not light, check black
wire for open and repair as necessary. If test lamp lights, replace coolant fan.
4.
If coolant fan does not operate with A/C and ignition switch ``On,'' and A/C operation is satisfactory, proceed as follows:
a. Remove A/C coolant fan relay, then connect a suitable test lamp between terminals A and C of connector. Ground diagnostic terminal. If test
lamp does not light, check light blue/black wire for open and repair as necessary. If wires are satisfactory, an ECM malfunction is indicated.
If test lamp lights, proceed to step b.
b. Jumper terminal B to terminal D using a suitable fused jumper. If coolant fan operates, replace A/C coolant fan relay. If coolant fan does not
operate, check dark green/white wire and black wire for open and repair as necessary.
5.
If coolant fan operates continuously with ignition switch ~``On'' the A/C ``Off'' but operating satisfactorily, proceed as follows:
a. Disconnect coolant fan switch. If coolant fan stops, replace switch. If coolant fan operation does not stop, check wire 335 for short to
ground, then proceed to step b.
b. Disconnect A/C coolant fan relay. If coolant fan stops, replace A/C coolant fan relay. If coolant fan does not stop, check black/red wire for
short to battery voltage.
6.
If coolant fan operates continuously with ignition switch ``Off,'' proceed as follows:
a. Disconnect coolant fan relay. If coolant fan stops, replace relay. If coolant fan does not stop, check black red wire for short to battery
voltage.