Century V6-173 2.8L VIN W FI (1987)
Heavy Duty Coolant Fan: 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.
6 Cylinder Models
On V6-173 VIN X, the coolant fan is controlled by the coolant fan switch and the A/C high pressure switch. The A/C high pressure switch closes
when the compressor is operating and there is an adequate refrigerant charge. On V6-173 VIN W, the coolant fan is controlled by the coolant fan
switch and the Electronic Control Module (ECM). The ECM will only turn on the coolant fan when it senses high engine coolant temperature or high
A/C pressure. The coolant fan switch or ECM can provide a ground path for the coolant fan relay and energize it. When energized, the coolant fan relay
contacts close and battery voltage is applied to the coolant fan. On V6-231 VIN B, two types of fan are used. These fans are controlled by either the
coolant fan relay, the coolant fan delay relay, the pusher coolant fan relay, the puller coolant fan relay or the A/C high pressure switch, depending on
specific application or engine requirement. On vehicles less A/C, the coolant fan relay is controlled by the coolant fan switch or ECM. For operation
with A/C, the coolant fan relay is controlled by the coolant fan switch, the A/C high pressure switch and the ECM. When one of these components
grounds the coil of the coolant fan relay, the contacts close and the fan comes on.
SYSTEM OPERATION
1.
If equipped with A/C, allow engine to operate at low idle, then move A/C selector lever to NORM. Coolant fan should operate.
2.
With engine coolant at normal operating temperature, operate engine at fast idle for several minutes. Coolant fan should begin operation before
coolant temperature gauge needle reaches H.
3.
If equipped with heavy duty coolant fans, fans will operate for short periods after engine is turned off and coolant is hot.
V6 VIN X
1.
Check applicable A/C or heater fuse, using a suitable fuse tester.
2.
If coolant fan does not operate when engine is warm or when A/C is ``On,'' proceed as follows:
a. Disconnect coolant fan switch connector, then jumper connector to ground, using a suitable fused jumper. Turn ignition switch ``On.'' 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 4.
3.
If coolant fan does not operate when A/C is on but operates when engine is warm and A/C compressor is satisfactory, proceed as follows:
a. Disconnect A/C high pressure switch. Connect a suitable test lamp between battery voltage and connector black wire. If test lamp lights,
proceed to step b. If test lamp does not operate, check black wire for open and repair as necessary.
b. Ground dark green/white wire at A/C high pressure switch, then turn ignition switch ``On.'' If coolant fan operates, replace A/C high pressure
switch. If coolant fan does not operate, check dark green/white wire for open, then repair as necessary and proceed to step 4.
4.
If coolant fan does not operate at all, proceed as follows:
a. Remove connector from coolant fan relay, then connect a suitable test lamp between terminal C and ground. Turn ignition switch ``On.'' 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. With coolant temperature switch connector jumped to ground, connect a test lamp from terminal C to terminal B of the coolant relay
connector. If test lamp lights, proceed to step c. If test lamp does not light, check dark green/white wire for open and repair as necessary.
c. Move test lamp from terminal C to terminal D of coolant fan relay connector. 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 d.
d. Connect a fused jumper between terminals D and A of coolant fan relay connector. If coolant fan operates, replace coolant fan relay. If
coolant fan does not operate, proceed to step e.
e. With fused jumper in place, remove coolant fan connector, then connect a suitable test lamp from terminal B to ground. If test lamp does not
light, check black/red wire for open and repair as necessary. If test lamp lights, proceed to step f.
f.
Move test lamp ground lead to terminal A of coolant fan connector. If test lamp does not light, check black wire for open and repair as
necessary. If test lamp lights, replace coolant fan.
5.
If coolant fan operates continuously with ignition switch ``On,'' proceed as follows:
a. Disconnect A/C high pressure switch, if equipped. If coolant fan stops, replace A/C high pressure switch. If coolant fan does not stop, or if
vehicle is not equipped with A/C, proceed to step b.
b. Remove coolant temperature switch connector, then turn ignition switch ``On.'' If coolant fan stops, replace coolant temperature switch. If
coolant fan operates, replace coolant fan relay.
6.
If coolant fan operates continuously with ignition switch ``Off,'' proceed as follows:
a. Remove coolant fan relay connector. If coolant fan stops, replace relay. If coolant fan continues, check black/red wire for short to battery
voltage.
V6 VIN W
1.
Check applicable A/C or heater fuse, using a suitable fuse tester.
2.
If coolant fan does not operate, proceed as follows:
a. Turn ignition switch ``On,'' then ground diagnostic terminal B at ALCL. If coolant fan operates, a malfunction is indicated. If coolant fan
