Regal V6-231 3.8L VIN L SFI (1990)
Chart C-12D-A Wiring Diagram
CIRCUIT DESCRIPTION:
The ECM and three relays are used to control the two cooling fans.
Low Speed Fan Operation - Low speed operation of both fans is controlled by the ECM. The ECM energizes the fan relay "B" (in the right hand power
center) for low speed fans when coolant temperature exceeds 101~C (214~F) or A/C requested. With ignition "OFF" the ECM will operate the cooling
fans at low speed if coolant temperature exceeds 110~C (230~F) and manifold air temperature exceeds 39~C (102~F) at time of key "OFF". The ECM
will keep the low speed fans "ON" with the key "OFF" for up to 2 minutes or until or until coolant temperature falls below 99~C (210~F).
High Speed Fan Operation - High speed fan operation of both fans is controlled by the ECM. The ECM energizes all three cooling fan relays when
coolant temperature exceeds 108~C (226~F) or A/C refrigerant pressure is sufficient to close the A/C head pressure switch (refrigerant pressure over
1380 kPa, 200 psi). High speed fans should not run with the ignition "OFF."
TEST DESCRIPTION:
Numbers below refer to circled numbers on the diagnostic chart.
1.
Low speed cooling fans may run up to 2 minutes with key "OFF."
2.
Verifies proper ECM control of fans.
3.
Checks for circuit 535 shorted to ground or a faulty fan relay.
4.
Checks for an A/C request signal to the ECM, which would cause low speed fan operation.
DIAGNOSTIC AIDS:
Check for a Mis-Scaled sensor refer to Coolant Temperature to Resistance Values on Trouble Code Chart 14. Replace sensor if Mis-Scaled. If not
Diagnose cooling system and radiator.
