3.8L & 5.7L CAMARO & Firebird: 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, from underhood fuse block.

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 3 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 3 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 commands low speed fans on under the following conditions:

• 3.8L
  
  
  • Engine coolant temperature exceeds approximately 221°F (105°C).
  • When A/C is requested and ambient temperature is greater than 50°F (10°C).
  • A/C refrigerant pressure exceeds 190 psi.
  • After vehicle is shut off, if engine coolant temperature at key-off is greater than 284°F (140°C) and system voltage is more than 12 volts. Fans will stay on for approximately 3 minutes.
• 5.7L
  
  
  • Engine coolant temperature exceeds approximately 226°F (108°C).
  • When A/C is requested and ambient temperature is greater than 50°F (10°C).
  • A/C refrigerant pressure exceeds 215 psi.
  • After vehicle is shut off, if engine coolant temperature at key-off is greater than 284°F (140°C) and system voltage is more than 12 volts. Fans will stay on for approximately 3 minutes.

PCM commands high speed fans on under the following conditions:

• 3.8L
  
  
  • Engine coolant temperature reaches 235°F (113°C).
  • A/C refrigerant pressure exceeds 275 psi.
  • When certain DTCs set.
• 5.7L
  
  
  • Engine coolant temperature reaches 234°F (112°C).
  • A/C refrigerant pressure exceeds 248 psi.
  • When certain DTCs set.