# Overheating - FANS?



## chasdwitt (Apr 1, 2008)

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Hey there,

I finally got my GXE smogged and back on the road (legally) I'm now having an overheat problem. Radiator in great shape, new water pump, hoses/belts/t-stat all good. I noticed that when idling with the A/C off that neither one of my fans up front are turning.

When I turn the A/C on, both fans go on. Can somebody explain to me when the fans are supposed to be running. Seems that at least ONE of the fans should be running full time.


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## smj999smj (Jan 1, 2006)

Neither of the fans will run if the ECM doesn't see the required temperature for them to run, unless the A/C is turned "on." Can give you more help if you give me a year to work with.


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## SPEEDO (Jun 9, 2003)

one fan will come on when it gets to temp, turn the a/c on and they both come on...
you might have trapped air in the system, but, as stated above, supply some vehicle info....


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## chasdwitt (Apr 1, 2008)

Sorry, 02 Sentra 1.8 GXE

So if the ECM is not seeing the temp reaching operating temp would the fix be to test/change out the temp sensor/sender...or the relay...or?

...and does the fan run continuously with the A/C on or just when it's cycling? I can cruise 70+ on the freeway and the temp is constant (air flow) but into traffic the needle starts to rise. Luckily I have not had it *OVER*heat, just hotter than anything usual.

...and shouldn't I get some sort of code if the engine is getting hot??

Are there 2 separate sensors as in 1 sender for the gauge and 1 sensor for the ECM??


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## SPEEDO (Jun 9, 2003)

the water temp sensor must be in water for it to work, make sure you do not have air pockets in the coolant system..... could be a cheap fix


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## chasdwitt (Apr 1, 2008)

SPEEDO said:


> the water temp sensor must be in water for it to work, make sure you do not have air pockets in the coolant system..... could be a cheap fix


I understand that. Is the sensor for the gauge the same as the sensor for the ECM/fan relay. My Jeeps constantly had issues with bleeding air...as simple as drilling a hole in the t-stat...and I installed a bleeder valve in the t-stat housing. 

I'm leaning towards a head gasket problem, only because when it does overheat the overflow is full...not boiling or bubbling...I don't see any tiny bubbles in the coolant, there is no crap in the coolant and no coolant in the oil. I suppose I have to get a tester for exhaust gases in the coolant. The coolant is nice and green. 

...any weird things to know about changing the head gasket or is a straight forward R&R?


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