Cooling fans

GP004

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I'm new here, so this might have been covered previously. If it has, please direct me to the solution as I don't know my way around the forum yet. I have a 2004 Grand Prix, NOT supercharged. The cooling fans come on when the A/C is turned on, but they don't come on automatically when the coolant temp rises. Any suggestions? Cooling fan controller? Relays? I can't find information anywhere on how to troubleshoot this. Thanks for the help! The car has a little over 120K miles and is otherwise in great shape. No other engine issues.
 

melsg5

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How high is the temperature?
Do you have a check engine light on?
 

GP004

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How high is the temperature?
Do you have a check engine light on?
No check engine light. The temp gauge is definitely above normal, but if I'm moving at highway speed it doesn't redline because of airflow through the radiator. No numbers, so I don't know the actual temperature. I do know that the fans don't come on automatically when the temp starts climbing. Thanks for getting involved with my problem.
 

melsg5

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Fans may not come on till 215 to 220 so without knowing actual temperature difficult to say if you have a problem.
Is this vehicle new to you?
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GP004

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Fans may not come on till 215 to 220 so without knowing actual temperature difficult to say if you have a problem.
Is this vehicle new to you?
I've had it almost 3 years. You know how it is when you get used to driving a car for a while. You get used to where the temp gauge looks all the time. It's been consistent forever, until a few months ago. It is definitely above what is usually is. I popped the hood and let it run and watched the gauge go up...no fans coming on. I don't know what temperature sensing device controls the fans. There is a part sold called the cooling fan controller. I haven't been able to find any information that tells how to test it or even where it is. It's got a sensor and several wires coming out of it. I acquired a Haynes shop manual. Got what I expected from it. Zip. :(
 

melsg5

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I've had it almost 3 years. You know how it is when you get used to driving a car for a while. You get used to where the temp gauge looks all the time. It's been consistent forever, until a few months ago. It is definitely above what is usually is. I popped the hood and let it run and watched the gauge go up...no fans coming on. I don't know what temperature sensing device controls the fans. There is a part sold called the cooling fan controller. I haven't been able to find any information that tells how to test it or even where it is. It's got a sensor and several wires coming out of it. I acquired a Haynes shop manual. Got what I expected from it. Zip. :(
You need something that will tell you the actual temperature and then you can determine if it's sufficiently high to tell the ECM to turn on the fan.
 

GP004

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You need something that will tell you the actual temperature and then you can determine if it's sufficiently high to tell the ECM to turn on the fan.
Let me rephrase my problem. My cooling fans don't come on when their supposed to. The engine gets hot. I'm looking for information about what exactly tells the fans to come on when they need to. I'm pretty sure that component is broken, but I can't find anything, anywhere to tell me what exactly it is, how to troubleshoot it, and replace it if necessary.
 

melsg5

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The ECM turns on the fans based on input from the temperature sensor.
Since they come on with AC, no fan motor problem or relay problem.
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Thanks! :) Would that be the same temperature sensor that sends a signal to the gauge? If that were the case it seems like the gauge would not show a reading. That's confusing to me, but I'm sure you're on the right track. I really appreciate the help.
 

melsg5

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Rockauto shows only one sensor. That isn't necessarily the problem. A scan tool is required to see what temperature the ECM is detecting.
 
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