Fan clutch always engaged

Tiny
YUKON JOE
  • MEMBER
  • 2006 NISSAN PATHFINDER
  • 4.0L
  • 6 CYL
  • 4WD
  • 160,000 MILES
When its bad I thought it wouldn't be engaged. Is it just stuck and needs to clean the spring or something? Sounds like a school bus all the time, hot or cold.
Saturday, February 15th, 2020 AT 9:32 AM

8 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This could be the fan clutch assuming you have the actual clutch type system. This vehicle has an option of either the clutch or motor driven.

Either way, the fan is commanded on by the ECM based on a couple inputs. The ECT is the main driver but if the AC is on, it will turn it on as well.

Here is a guide that goes through the detail about why a clutch will cause the roar of the fan:

https://www.2carpros.com/articles/fan-clutch-symptoms

If you have a motor fan then we need to monitor the engine coolant temp and see what it is telling the ECM. If this is correct then you could have an issue with the ECM itself. This is more rare then the other issues but it could still be the issue.

If you have the clutch type, then I suspect it is the clutch itself.
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Saturday, February 15th, 2020 AT 10:26 AM
Tiny
YUKON JOE
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It's a clutch fan. Also has electric o e in front of A/C pump on radiator. I read the article I just do not understand. It says if it doesn't turn easily it's locked up, but if it turns to freely it's bad and not going to work. It doesn't make sense because it turns easy by hand but is engaged and sounds like a "jet plane" all the time.
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Saturday, February 15th, 2020 AT 8:11 PM
Tiny
KASEKENNY
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Okay. The article does not cover 100% of the types of failures, just the most common. So in most cases if the fan doesn't spin easily then the clutch is stuck on.

It could be the fan clutch but we have to rule out everything else first since yours doesn't match this description.

Do you have a scan tool to see what the engine cooling temp sensor is saying in the PCM? Or if we have codes?

I suspect if the ECT sensor is failed it would be reading improperly causing the PCM to turn the fan on all the time.
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Sunday, February 16th, 2020 AT 9:41 AM
Tiny
YUKON JOE
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I have a scan tool, but what do you mean by turning on the fan? Its not electric it's a manual clutch fan.
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Sunday, February 16th, 2020 AT 10:27 AM
Tiny
KASEKENNY
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You said your fan was easy to spin and felt free and not locked up. This would point to the fact that the clutch is not locked up and holding the fan on when the engine is running. Take a look at the attachment. That is what I meant by turning the fan. When you turn it by hand with the engine off, it should spin freely and not be hard to turn.

The fact that your clutch does not sound like it is locked up we need to find out why it then engages when the engine is turned on. Usually this is because it is commanded on by the engine controller. This means either the engine controller is the issue or something is telling the controller to do that when it shouldn't. The only thing the engine controller looks at to determine this is the ECT so let's just turn the key on after sitting overnight and see what the ECT temperature is reading. It should be very close to the ambient temperature and intake temperature. Let me know what each three are after it has been sitting for a while and we can go from there. Thanks
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Sunday, February 16th, 2020 AT 6:25 PM
Tiny
YUKON JOE
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There is nothing electronic to this clutch fan, what do you keep saying that for?
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Monday, February 17th, 2020 AT 9:45 AM
Tiny
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Also this one is filled with fluid, not spring operated.
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Monday, February 17th, 2020 AT 10:04 AM
Tiny
KASEKENNY
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Sorry. The service info for this vehicle says that your vehicle has the electric fan on the radiator for the AC condenser and then has the cooling fan as an electric clutch (see attached). That means then ECM would apply the clutch and remove it.

If yours has a viscous clutch then that explains the issue you are seeing.

The non ECM controlled are the two types you are mentioning. One is spring controlled. As the spring heats up it begins to engage the clutch until it is fully applied.

The other is fluid filled or a viscous clutch. These too have a spring which allows the silicone to leave the reservoir in the front of the clutch and engage the blades. The spring moves as it get hotter.

Here is a video that gives more detail on this:

https://youtu.be/UwM4OqsLek4

Since you are able to spin the clutch by hand, that shows the spring inside has stopped moving which opens and closes the opening for the silicone to engage the clutch. That means when the engine turns on, the centrifugal force causes the silicone to engage the clutch then when you shut the vehicle off, the silicone drains back and disengages the clutch allowing you to spin it by hand.

Long story short. It needs to be replaced.
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Monday, February 17th, 2020 AT 6:37 PM

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