Sunday, December 11, 2011

Replace Fan Relay but still Radiator cooling fans not working?

Radiator cooling fans runs when engine over heats and temperature gauge rises.
Verify that the fans work by unplugging them and run jumper wires to the fan(s) from the battery, and not from the other fan or anywhere else. If they run, your problem lies elsewhere. If either does not run, it's the motor.
The PCM commands Low Speed Fans ON under the following conditions:
• The engine coolant temperature exceeds approximately 106°C (223°F). • The A/C refrigerant pressure exceeds 1310 kPa (190 psi). • The vehicle is shut off when the engine coolant temperature 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:
• The engine coolant temperature reaches 110°C (230°F). • The A/C refrigerant pressure exceeds 1655 kPa (240 psi). • When certain DTCs set. The primary fan (Fan#1) is protected by a 30amp fuse and the secondary fan (Fan#2) has 15 amp. So it's not surprising the secondary fan fuse blew when you connected the primary fan on the secondary connector. On a V6 engine, there is additional ground fuse (30amp) for the secondary fan circuit, also at the underhood fuse block.
The information above shows the two modes of operation of the cooling fans, as to when they should work, so that you may have better understanding. Since you have changed all the 3 cooling fan relays, you should also check the fuses, the power, ground, and the condition of the fan connectors.
The Powertrain Control Module (PCM) controls the on and off of the relays, depending on the inputs provided by the engine coolant sensor (ECT) and a/c pressure sensor.
At low speed mode (106degC), Fan#1 relay clicks on, and both fans will work at low speed. In case one of the fans is defective, the other will not spin as well. If left on this condition, naturally the engine will get hotter, until it reaches 110degC which will be the high speed turn-on point.
At high speed mode, the other 2 relays will also click on. This time each fan motor will receive full 12v power and expected to roar at high speed.
The condition of the coolant, the ECT sensor, and the PCM itself plays an important role in the proper operation of the cooling fans. A faulty ECT sensor will not give the proper signals to the PCM, and a faulty PCM may not give the required control signals that it's programmed to be.
In case of an ECT or PCM issues, a scan tool can effectively monitor the signals coming from this components. As for the rest of the circuit, you can check it the usual conventional method.

This details will help you.

If you need dis-assembly or replacement instructions for any other auto/car part, or you want to ask question related to your car/truck jeep problem then please leave the comment with your details, so I can provide you the required instructions and solutions.

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  1. I have a 2004 Dodge Intrepid 2.7 and I'm getting OBDII Code P0480 and that's all. Both fans will turn on when the A/C is on. When I turn it off, no matter how hot the engine is, the fan will not come on at all. I've already replaced the Radiator Fan Relay. Same results. Any help would be greatly appreciated.

  2. When the engine is hot,try giving direct power to the fan via 12 volt external battery source and bypass the relay and see.-----------
    Now if the fan comes on that way,this clears that relay is not functioning right,but if fan is still not coming on when given direct 12 volt then its weak fan motor.-------------
    The relay is controlled by computer module.If its confirmed that relay is working fine,then module has to be inspected.May be its not getting the indication that engine is hot.

    When the engine gets hot,the the sensor triggers the module and module gives command to relay and relay lets the fan run.But if temp sensor is not running or module is not functioning right then relay will not get the command to start the fan.

    Getting this things checked will help.