cooling fans coming on late - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-11-2007, 01:59 PM   #1
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Default cooling fans coming on late

When going through town or in traffic the cooling fans dont turn until the temp guage gets to the last line before the red I think that would make it 240 degrees but im not sure. What should I do, Ive already installed a 180 t-stat and it works great but what should I do about in town. This is where the power loss starts in. At around 200 it starts to lose some of its power.
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Old 06-11-2007, 03:54 PM   #2
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First thing to do is get an actual scan gauge on the car to determine if the temp gauge in the cluster is reading 240F when the actual temp is 225F. We have seen many cases of this.
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Old 06-12-2007, 01:33 PM   #3
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Its reading correct cause the temp is at 180 going down the highway
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Old 06-12-2007, 01:49 PM   #4
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First of all, please read the signature requirements topic in NOTICE.

Secondly, you have TWO coolant sensors. One for the gauge, one for the PCM to control the fans and other temperature dependent functions. My first suggestion would be to check the resistance of both sensors at the same temperature (one cold, one hot comparison between the two) and make sure they're reading close to the same.

Temperature vs Resistance values are listed in Techinfo for IAT and ECT sensors.

Thirdly, if your car gets that hot, simply turn on your AC. After you do, pop the hood and visibly verify that both fans came on high. That'* a default state the PCM commands when the AC turns on.
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Old 06-12-2007, 02:15 PM   #5
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I'm drawing on my experience with a 95. The gauge running down the road would read correctly...around 180. When it got hot..I would see 240 before the fans came one. Like you ....I figured there was a problem. Using a scan tool....I found that my gauge was in accurate. It'* not a linear issue where we can say because at 180 the gauge reads 180 therefore it'* accurate.

Also at NEBF Maymybonneliveforever found out his gauge is inaccurate.

We've seen many cases and my suggestion would be to check it with a scan tool in order to know for sure what the actual temperature is reading at the PCM.
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Old 06-12-2007, 02:19 PM   #6
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Checking with a scantool will only tell you what the other ECT THINKS the temp of the coolant is. It could be bad just like the one for the gauge.

To clarify (for Series 1):

1 ECT tells the PCM what it thinks the coolant temp is.
1 ECT tells your gauge what IT thinks the coolant temp is.
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