Today while adding coolant to my car, I noticed that once the car reached running temperature only the fan on the passenger side had turned on. I checked the connection and that was fine, the fuses were also fine. Is this normal or should I look at replacing the fan motor?

2003 Infinity I35 V6 3.5L

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    I don't know if it's true on your Infiniti, but most vehicles only turn on one fan at one temperature, then if they reach a higher, predetermined temperature, it will kick on the second. The second fan may also be used for when the A/C compressor is kicked on to cool the condenser core. Jun 18 '16 at 16:06

The Engine Control Module has multiple outputs to control at least 3 different relays that control the two fans on the radiator/condenser area.

Each fan has 4 wires, and a HI and LO speed.

The exact control strategy I could not discover, but the ECU uses a variety of input signals and internal variables to determine how much "fan" should be turned on for each occasion. Speed, coolant temperature, air temperature, and air conditioning inputs are used to operate the fans in a thermal control strategy.

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