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2005 gmc sierra radiator fan staying on

I have a 2005 gmc Sierra 1500 and the radiator fans are staying on after the truck is off had to unplug them and it still drained my battery dead

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  • nvstein4
    nvstein4 Dec 02, 2012

    I put a new relay and coolant temp sensor and the fans still run with truck off

  • teds repairs
    teds repairs Dec 02, 2012

    you have 2 things left the fans or the computer

  •  ali abbas
    ali abbas Dec 02, 2012

    only one fan is coming on or both the fans? is it running is full speed or slow ? i am going to look at the wiring diagram reply my questions mean wile.

  • nvstein4
    nvstein4 Dec 02, 2012

    Both fans and they are on full speed

  •  ali abbas
    ali abbas Dec 02, 2012

    it seems like there are three fan relay which one did you changed

  • nvstein4
    nvstein4 Dec 02, 2012

    When i unplugged number one the fans shut off i checked all three but number one is what is kicking them on

  •  ali abbas
    ali abbas Dec 02, 2012

    ok hold on did you change the number one only ??? try taking all three out then put the number one in check if the still come on ? one circuit on this acts like a seriese circuit.

  •  ali abbas
    ali abbas Dec 02, 2012

    just use the new one in each slot one at a time. if the problen continues there could be a wire grounding some where. and its a ground wire which brings the signal from the pcm. you can also ckeck the out put signal from the pcm to the high speed fan relay if the computer is giving the ground signal then its the pcm. now keep this in mind the if there that wire is shoet to ground the reading you get from the pcm will not be good in order to get the correct reading you will have to cut the wire near the pcm and check if there is any ground signal comming out of it . its getting complicated god helps you. i hope its the relay.



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Check the repays that run the fans or the coolant temp sensor

Posted on Dec 02, 2012


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Its coolent temp sensor for the radiator fan check it if not that a bad radiator fan relay.

2005 gmc sierra radiator fan staying on - 12_2_2012_10_33_30_pm.gif

Posted on Dec 02, 2012


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Posted on Jan 02, 2017


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SOURCE: I have a 2005 GMC Sierra 1500 with 100,000 miles

On most GMC Models and CHevy for that matter. There is a hole towards the bottom but still on the side of the radiator. I had to run a small hose from that port to a container on the ground. I did this for a few times and it really helps keep your garage floor clean and clear. I also found it to be a bit of a nuissance to flush the radiator.

Posted on Oct 24, 2009


Corey Shubart

  • 146 Answers

SOURCE: My Power window on my 2003 GMC Sierra 1500 Truck

if your main switch panel still works the passenger window and if door locks still work probaly bad window motor

Posted on Oct 21, 2009


Harvey N Tawatao

  • 3854 Answers

SOURCE: 2004 GMC Sierra 4dr truck. the fan does not work

The switch or the wire harness at the blower motor has gone bad. The highest setting 5 has no resistor, so the blower runs on high but the high current flow ends up burning up the switch's contact on that setting or the resistor wire harness at the blower motor has gone bad. Common would be the switch it self, if the switch is good. Then it's going to be the wire leads at the speed resistor by the blower motor under the glove box by the passenger leg compartment. Keep me posted, be glad to help you get your Sierra running 100% again soon.

Posted on Jan 06, 2010


  • 167 Answers

SOURCE: the fans begind me radiator willnt shut off in my 2005 gmc sierra

If you read the label on the radiator shroud/fan cowls, you will see that it says "Warning--These fans may operate at any time, even if the ignition is off."
This means that the computer monitors the coolant temperature through the sensor in the water neck, block, or radiator, and turns the fans on if any of them reports (true or not) that the coolant is too hot.
Obviously, there is nothing wrong with the fans, because they run.
First, check your coolant level; if it's too low, then the engine actually boils the coolant in the radiator, causing it to flash over to steam, which is hotter than the thermostat is set to allow the engine to operate. Check this in the radiator itself, not the coolant bottle, with the engine of course cold at the time of your check.
You have, at the least, a false signal from one of these sensors.
You could also have a faulty fan relay in the distribution box under the hood on the driver's side of the vehicle.
You could also have a faulty ECM (hope it's not that one...$$$).
Please let me know if this helps you, and remember to vote/comment.

Posted on Feb 16, 2010

Salvador Quintanilla

  • 1608 Answers

SOURCE: 2004 gmc sierra 1500 blower motor location

The blower motor is on the passengers side under the dash.You might have to remove the a lower panel.This is the insulator panel.If the blower works at all just turn it on and follow the noise.Hope this helps.Good luck.

Posted on Apr 08, 2010

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