5.7L Corvette: Description

Engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. Relays are arranged in a series/parallel configuration that allows Powertrain Control Module (PCM) to operate both fans together at low or high speeds. Cooling fans and fan relays receive battery voltage and ignition 1 voltage from underhood electrical center.

During low speed operation, PCM supplies ground path for low speed fan relay through low speed cooling fan relay control circuit. This energizes cooling fan 1 relay coil, closes relay contacts, and supplies battery voltage through cooling fan motor supply voltage circuit to left cooling fan. Ground path for left cooling fan is through cooling fan 3 relay and right cooling fan. Result is a series circuit with both fans running at low speed.

During high speed operation, PCM supplies ground path for cooling fan 1 relay through low speed cooling fan relay control circuit. After a 3-second delay, PCM supplies a ground path for cooling fan 2 relay and cooling fan 3 relay through high speed cooling fan relay control circuit. This energizes cooling fan 3 relay coil, closes relay contacts, and provides a ground path for left cooling fan. At the same time, cooling fan 2 relay coil is energized closing relay contacts and provides battery voltage on cooling fan motor supply voltage circuit to right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. Result is a parallel circuit with both fans running at high speed.

PCM will command low speed operation on at 226°F (108°C) and off at 217°F (103°C).

PCM will command high speed operation on at 235°F (113°C) and off at 226°F (108°C).