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Does anybody know how to keep the radiator fan from coming on when I am not using the air conditioning or defroster in the winter when the temperature is very cold? Seem pretty foolish to have the radiator fan on when the outside temperature is well below zero.
 

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Does anybody know how to keep the radiator fan from coming on when I am not using the air conditioning or defroster in the winter when the temperature is very cold? Seem pretty foolish to have the radiator fan on when the outside temperature is well below zero.
It seems foolish to disenagage something that was designed the way it was. Out of curiosity why would anybody even care outside of just the smallest mpg gain.
 

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Yea pull the relay lol
Yes, and be sure to tell that to the Nissan dealer when he tells you that you have a blown head gasket.


The fan is serving a function, not matter how cold outside it is. Leave it alone if you value your warranty!


Have a good day.
 

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Amen. Outside temp has an affect on engine cooling, but is not sufficient by itself.
 

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Hello JoeD,

I'll copy and paste the answer I provided last year when you asked the same question. If you have further questions after reading this, just let me know. Good Luck.


Just to add my 2 cents...

(I'm assuming the original poster's 10 degree temperature reference was in Fahrenheit.)

The Engine Control Module (ECM) controls radiator cooling fan speed corresponding to vehicle speed, engine coolant temperature, refrigerant pressure, and the air conditioner ON signal. The control system has 4-step control [High/Middle/Low/Off].

The attached diagram shows how rad fan speed varies with these four inputs. This confirms what wtgkb8 has pointed out, air conditioning ON signal will cause the rad fan to operate at any speed including zero. In turn, the air conditioning ON signal will be called for when the HVAC mode setting is "defrost" or "floor/defrost", regardless of a/c button setting.

What is interesting is that the air conditioning compressor has low temperature protection:

  • When intake sensor detects that front evaporator fin temperature is 2.5°C (37°F) or less, A/C auto amp. requests ECM to turn A/C compressor OFF, and stops the A/C compressor.
  • When the front evaporator fin temperature returns to 5.0°C (41°F) or more, the A/C compressor is activated.
So if I'm reading this correctly, the a/c compressor should not come on at 10 degrees F as per the original poster's description, even if defrost or floor/defrost is chosen, which in turn means the rad fan should not come on at that temperature.

I may be missing something here, so perhaps ensure the a/c is indeed off and see if the rad fan runs at a 10F startup. If it does, there may be a gremlin in the works and a visit to the dealership is warranted.

By the way, I personally would not unplug the rad fan for the winter season. The engine coolant also serves the oil cooler and the CVT cooler. If one became stuck in traffic, even in the winter season, engine oil and CVT oil temperatures could rise to unacceptable levels without any warning to the driver. But that's just me.

Good luck!​
 

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