Somerset Regal L4-151 2.5L (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 SOMERSET REGAL & OLDSMOBILE CALAIS
SYSTEM DESCRIPTION
4-151 Engines
A cooling fan relay is used to control the cooling fan. When coolant temperature is high, the cooling fan temperature switch closes and provides a path
to ground for the relay coil. The contacts close applying battery voltage to the fan. On vehicles equipped with A/C, the cooling fan runs when the
compressor is on. The coil of a separate A/C cooling fan relay receives battery voltage through the A/C mode selector and the pressure cycling switch
and is grounded through the ECM. When the compressor clutch is on, the ECM grounds the coil of the separate A/C cooling fan relay whose contacts
close to ground the cooling fan relay coil. The cooling fan relay is energized and battery voltage is applied to the cooling fan causing it to run. A diode is
connected across the cooling fan relay coil to absorb voltage spikes.
SYSTEM CHECK
4-151 Less A/C
1.
Run engine at fast idle for several minutes. Cooling fan should turn on before coolant temperature indicator on instrument panel comes on.
4-151 With A/C
1.
With engine at normal operating temperature and running at slow idle, set A/C mode selector to NORM position. Cooling fan should turn on.
2.
Set A/C mode selector to OFF position. Run engine at fast idle for several minutes. Cooling fan should turn on before coolant temperature
indicator on instrument panel comes on.
