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goodwrench9124
goodwrench9124, ASE Certified Technician
Category: Chevy
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2003 chev malibu 3.1 cooling fans wont come on. we ...

Resolved Question:

2003 chev malibu 3.1 cooling fans wont come on. we replaced intake man gskts, wtr pump, therm, coolant, bled system well. car wasnt overheating but we tore it down beacause we discovered a liltlle oil in the coolant overflow tank....just small beads...now she overheats beacause the fans only come on w a/c. had a couple malibus before same game.   aaaargh
Submitted: 9 years ago.
Category: Chevy
Expert:  goodwrench9124 replied 9 years ago.

Hello, fairly simple system, there are three relays and two fuses for the cooling fans. and the power control modules turns the fans on and off. if both the fans dont work, check the fan mode relay. this relay controls both the fans. here is a wiring diagram to help. also the pcm simply provides a ground for the relays, to turn on fans. there also is a ground fuse for the cooling fans check this fuse 15 amp in the under hood fuse block.

FIGURE Cooling Fans(c)


Object Number: 783086  Size: FS

Cooling Fan Control

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood junction block. The ground path is provided at G103.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan s/p relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

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

The PCM commands Low Speed Fans on under the following conditions:

  • Engine coolant temperature exceeds approximately 106°C (223°F).
  • A/C refrigerant pressure exceeds 1310 kPa (190 psi).
  • After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:

  • Engine coolant temperature reaches 110°C (230°F).
  • A/C refrigerant pressure exceeds 1655 kPa (240 psi).

 

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