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Electric fan not working

Tiny
STEELERDYNASTY
  • MEMBER
  • 2002 JEEP GRAND CHEROKEE
  • 4.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 186,750 MILES
Electric fan is not working. I have a mechanical clutch fan also installed and it does work. I have an automotive logic probe and it will only turn green when I touch either wire. The electric fan does not come on at all, even when touching the wires directly with the logic probe. Am I doing something wrong? How do I test the fan vs testing the relay in hopes of isolating and repairing the problem?
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Friday, March 30th, 2018 AT 11:03 PM

13 Replies

Tiny
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I just read the "how cooling fans work" link on this site. Is it possible that my engine is not running hot enough to engage the fan?
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Saturday, March 31st, 2018 AT 6:56 AM
Tiny
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This car has a hybrid cooling system that uses both mechanical fan and electric, pulse width modulated electric fan. One fast way to determine if it is working is to turn on the AC and the fan should come on. If not the system has a solid state, electronic relay located on the left frame rail, behind the radiator. It is difficult to access as you have to remove the front bumper, grill and vacuum reservoir.
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Saturday, March 31st, 2018 AT 8:29 AM
Tiny
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So with A/C on, I should see both fans running no matter what correct?

So with A/C off, only clutch fan should turn correct?
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Saturday, March 31st, 2018 AT 8:48 AM
Tiny
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No, that is not what I said. What I mean is that the only time you can rely on seeing the electric fan is when the AC is on. Without the AC you may never see it come on.
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Saturday, March 31st, 2018 AT 8:53 AM
Tiny
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Forgive me, but I am a novice.

Car on, A/C on what other circumstances need to exist for the fan to turn on? How long should I watch and wait before deciding that it is not working?
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Saturday, March 31st, 2018 AT 9:48 AM
Tiny
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I gave you the simplest possible way to determine if the fan is working or not. The other way is using a bidirectional, professional scan tool to turn it on with the tool.

From the service manual

Description:
The pulse width modulated (PWM) radiator cooling fan relay is located behind the front bumper fascia below the right headlamp.

Operation:
The PWM relay is used to control the speed of the electric radiator cooling fan. It allows for multiple fan speeds. This allows for improved fan noise and A/C performance, better engine cooling, and additional vehicle power.
PWM relay operation is controlled by the Powertrain Control Module (PCM). To operate the PWM relay, the PCM looks at inputs from:
Engine coolant temperature.
Ambient temperature from the body controller.
Vehicle speed.
Transmission oil temperature.
A/C switch position (A/C request).
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Saturday, March 31st, 2018 AT 9:52 AM
Tiny
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Left the car running with the AC on high for about twenty minutes, no movement on electric fan. Swapped out relay, ran for another ten still no movement.
Fan spins freely with engine off.
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Saturday, March 31st, 2018 AT 10:55 AM
Tiny
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I do not know how you could have accessed the correct relay that fast but it is time for some troubleshooting which may require the use of a bidirectional scan tool.
Here is the wiring diagram.
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Saturday, March 31st, 2018 AT 11:01 AM
Tiny
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I have done it before, and the spot is still open. Mounted correctly to the body so it does not overheat and melt the wires.
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Saturday, March 31st, 2018 AT 12:31 PM
Tiny
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Wires do not melt from overheating relays. The connectors can overheat due to resistance in the connection though.
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Saturday, March 31st, 2018 AT 12:34 PM
Tiny
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That is what I meant. It is why I had to replace it last time.

As an aside, I replaced my fan clutch within the last three weeks. Prior to even realizing I had a problem, I was not having any overheating issues. That has to be encouraging right?
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Saturday, March 31st, 2018 AT 12:41 PM
Tiny
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Okay, I am going to concede defeat. If/when I decide to replace the fan and/or motor, is it possible to do without removing the clutch fan? When I replaced the clutch fan, I was not able to remove it until I also removed the electrical fan. I am really hoping the electric fan can be replaced without removing the clutch fan.
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Sunday, April 1st, 2018 AT 11:52 AM
Tiny
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Yes, you do have to remove the fan clutch.
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Sunday, April 1st, 2018 AT 1:04 PM

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