Cooling fans not working

Tiny
JORDAN E LINDIAKOS
  • MEMBER
  • 2007 PONTIAC G6
  • 3.5L
  • V6
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
I was recently stuck in traffic and noticed that the temperature was getting high. Twenty minutes later had some steam coming from under the hood because the coolant reservoir was overflowing (seeping out of the cap). I replaced the water pump, changed the belt. I noticed that only one of the two fans for the radiator are turning on. I swapped the relays and fuses for the fans and one will turn on when the car is warm or the A/C is on. There are three relays, one for each fan and one for the fans to run together, from what I understand. Not having another relay that was the same as that one to swap with, I also bought a new relay to replace that one. So ultimately my questions are: Is this normal, for only one fan to be kicking on with the A/C full blast and the car at mid-range temperatures? At what temperature should the two fans turn on? Is there a way to trick the car so I can see if the second fan works before going further with troubleshooting?
Saturday, February 16th, 2019 AT 10:57 AM

10 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Both fans should work.

https://www.2carpros.com/articles/engine-overheating-or-running-hot

To test them, you need a scan tool that can manually turn them on.

Did you replace the thermostat as well when you did the water pump?

https://www.2carpros.com/articles/how-an-engine-thermostat-works

Do you have a voltmeter to do some checks?

Roy
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Saturday, February 16th, 2019 AT 12:20 PM
Tiny
JORDAN E LINDIAKOS
  • MEMBER
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So both fans should be on when the A/C is on max? I just let my car run for about an hour, mainly sitting in the driveway and then a twenty minute round trip around town. The car was just shy of reaching 225 degrees, about midway on the temperature gauge. When I got home I popped the hood and neither fan was on and the coolant reservoir looked to be full to the top and leaking out of the bottom. There is a small molded hole that it was coming out of. When I was replacing the water pump and had to fill the reservoir I could not see a leaking. I assume this "leaking" is something designed to prevent the reservoir from becoming too pressurized? I do not have the tools that you referred to unfortunately.
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Saturday, February 16th, 2019 AT 1:33 PM
Tiny
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No, nothing should be coming out of the tank at all.

Try removing the connector for the coolant sensor by the thermostat with the key on.

The fans should both come on.

Again, did you replace the thermostat?

Roy
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Saturday, February 16th, 2019 AT 1:36 PM
Tiny
JORDAN E LINDIAKOS
  • MEMBER
  • 6 POSTS
I did not replace the thermostat. I will try to remove the connector for the coolant sensor. I truly appreciate the advice and quick responses.
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Saturday, February 16th, 2019 AT 1:57 PM
Tiny
ASEMASTER6371
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  • 52,797 POSTS
You are welcome.

Always glad to help.

Change that thermostat.

Roy
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Saturday, February 16th, 2019 AT 2:01 PM
Tiny
JORDAN E LINDIAKOS
  • MEMBER
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I wasn't thinking it was the thermostat originally. When I was sitting in traffic and the car was running hot, temperature gauge 3/4 to max about 240°, the car was rapidly cooled when I got out of traffic and was moving, temperature dropped to less than 200. I figured if the thermostat wasn't opening it wouldn't cool down that much or quick. Am I wrong to think that? I am no professional mechanic by any means so I am just assuming.
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Saturday, February 16th, 2019 AT 2:55 PM
Tiny
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  • MEMBER
  • 6 POSTS
I unplugged the coolant sensor, I think, and neither fan turned on. The driver side fan turned on with the A/C like before though. The coolant sensor is right next to the radiator line where the thermostat is correct? Or perhaps I unplugged some other sensor.
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Saturday, February 16th, 2019 AT 2:58 PM
Tiny
ASEMASTER6371
  • MECHANIC
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It is a two wire sensor by the thermostat housing.

If the thermostat is only opening a small amount it could do this.

See if you can get a test light or voltmeter and Then we can do some checks.

Roy
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Saturday, February 16th, 2019 AT 3:12 PM
Tiny
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Thanks Roy. I'll start with just changing the thermostat tomorrow morning and see where things go from there. I appreciate your knowledge and advice in this.
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Saturday, February 16th, 2019 AT 3:16 PM
Tiny
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You are welcome.

Always glad to help.

Roy
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Saturday, February 16th, 2019 AT 3:17 PM

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