Having a problem with my truck over heating while at an idle. Fans will not turn on but if i turn on the AC the fans come on and the temp goes down. I have also replaced the thermostat and the fan control relay to no avail. So I was just wondering if yall could maybe give me some insight to what makes the fans come on when the AC is off. Or possibly the solution to the problem.

 

Possibly coolant temperature sensor. Controls when the fans come on without A/C.

 

Forgot to mention i also just changed the temp sensor.

 

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> stokea,

Possibly a faulty temp sensor? The water pump is another thing to consider.

Louis
GM Customer Service

 

At what temp is the fans suppose to come on if the ac is off

 

Is the truck actually overheating and coolant overflowing? or you looking at the gauge, which may or may not be accurate?

The fan won't come on until just before the truck overheats...about 230°

 

Temp sensor as posted turns one fan on as needed. If a/c is selected it will turn on the other fan. Odd that both fans only come on with a/c. I'd look more into the interface of the fan control with a/c, with that as I ALWAYS suggest anyone wanting to work, mantain thier own vehicle get a CSM.