Somerset V6-181 3.0L (1986)
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 SOMERSET REGAL & SKYLARK
DESCRIPTION
On 4 cylinder models, the coolant fan is controlled by the coolant fan relay. The coolant fan temperature switch closes when coolant temperature is
high, providing a path to ground for the relay coil. The relay contacts close to apply battery voltage to the fan. On vehicles equipped with A/C, the
coolant fan also operates when the compressor fan is on. The A/C relay, controlled by the ECM, supplies battery voltage through the A/C function
selector and pressure cycling switch. When the A/C compressor clutch is on, the ECM turns on the A/C coolant fan relay, then its contacts close to
ground the coolant fan relay coil. The coolant fan relay is energized, and its contacts apply battery voltage to the fan. On 6 cylinder models, a two
speed puller coolant fan and single speed pusher fan are used. The fans are turned operated by coolant fan relays which have two coils and two
independent sets of contacts. For low speed operation, the Lo speed relay coil is grounded through the ECM or the low speed contacts of the A/C high
pressure switch. The ECM grounds the coil when vehicle speed is less than 45 mph and engine coolant is warm. For high speed operation, the Hi speed
relay coil is grounded through the Hi speed contacts in the A/C high pressure switch or the coolant fan temperature switch. The pressure switch Hi speed
contacts close at a refrigerant pressure higher than the pressure that closed the Lo speed contacts. The coolant fan temperature switch closes when
coolant temperature is high. With the Hi speed relay coil grounded, the associated contacts close and battery voltage is applied to the heavy duty coolant
fan that operates at high speed.
6 Cylinder Models
1.
Check coolant fan related fuses, then on models less A/C, proceed as follows:
a. If pusher coolant fan does not operate, connect a suitable test lamp between terminals 1 and ground and terminals 5 and ground. If test lamp
does not light, repair or replace fusible link F, engine fan fuse or related wiring. If test lamp lights, proceed to step b.
b. Connect the test lamp to terminal 4. When engine temperature is above 230 degrees F, and test lamp does not light, disconnect coolant fan
temperature switch connector. Connect a suitable jumper from light green (536) wire to ground. If test lamp lights, replace temperature
switch. If temperature switch is satisfactory and test lamp lights on terminal 4, replace pusher coolant fan. If temperature switch is satisfactory
and test lamp does not light on terminal 4, replace pusher coolant fan relay.
c. If puller coolant fan does not operate, check fusible link F and engine fan for open and repair as necessary. If both are satisfactory, proceed
to step d.
d. If puller coolant fan does not operate at low speed, connect a suitable test lamp to terminals A and B of connector C108. If test lamp lights
on terminal B but not A, replace coolant fan resistor.
e. If puller coolant fan does not operate in high, check for pusher coolant fan operation. If pusher coolant fan is operating, check black/pink
(533) wire for open and repair as necessary.
2.
Check coolant fan related fuses, then on models with A/C, proceed as follows:
a. If coolant fan temperature switch is satisfactory, both the pusher coolant fan and puller coolant fan will operate on high when A/C switch is
turned on. Disconnect A/C high pressure switch connector and connect a suitable jumper wire from light green/black wire to ground. If both
fans operate, replace A/C high pressure switch or repair open in black/white wire (450).
COOLING FAN, REPLACE
1.
Disconnect battery ground cable.
2.
Disconnect wiring from fan motor and frame.
3.
Remove fan assembly from radiator support.
4.
Reverse procedure to install.
