Cooling System: Description and Operation

CIRCUIT OPERATION:
Two coolant fans, wired In parallel, operate whenever cooling is required.

The powertrain control module (PCM) has two coolant fan control terminals: one for high speed and one for low speed. When the PCM's low speed control closes at connector C3, terminal C4, it grounds the low speed coolant fan relay coil. When the ignition switch is In the RUN position and the relay contacts close, voltage is supplied to the coolant fans. The voltage drops across the coolant fan resistors, causing the LH coolant fan to run at low speed. The RH coolant fan also runs, but at high speed because the coolant fan resistors are bypassed. The PCM's low speed output is turned on when coolant temperature reaches 100°C (212°F).

High speed operation is similar to low speed operation. When coolant temperature reaches 108°c (226°F),the PCM's high speed control closes at connector C3, terminal C3, grounding the high speed coolant fan relay coil. The relay contacts close and both fans run at high speed since the PCM's low speed control remains closed. When A/C head pressure reaches 1445 kPa (210 psi), the A/C pressure fan switch closes, grounding PCM input connector C1, terminal D9. This also causes the PCM high speed control to close, and both coolant fans run at high speed.