My coolant fan stays on?

Tiny
TRUCKWES
  • MEMBER
  • 2004 MERCURY MARAUDER
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 84,000 MILES
My coolant fan stays on. I change both temperature sensors. Thermostat and bled the system. My temp gauge take about 10 minutes to move to half. Heat is okay, what could be the problem?
Thursday, January 30th, 2025 AT 1:19 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,622 POSTS
This can only be one thing, the fan control driver inside the PCM is stuck on, I would get a rebuilt unit and replace it, you can get a preprogrammed unit by searching Google or Ebay. Here is how the repair job is done. Check out the images (below). Please let us know what happens.
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Friday, January 31st, 2025 AT 10:52 AM
Tiny
TRUCKWES
  • MEMBER
  • 28 POSTS
  • 2004 MERCURY MARAUDER
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 87,000 MILES
Radiator fans stay on. Before the engine warms up. Change temperature sensor and thermostat maybe computer. Where is the location?
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Sunday, February 9th, 2025 AT 5:08 PM (Merged)
Tiny
KEN L
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Did you see my response?
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Sunday, February 9th, 2025 AT 5:08 PM
Tiny
TRUCKWES
  • MEMBER
  • 28 POSTS
The coolant fan comes on as I start the car?
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Tuesday, February 11th, 2025 AT 1:45 PM
Tiny
KEN L
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Yes, I would check the wiring between the sensor and the PCM, here is a guide and the wiring diagrams so you can see how the system works and which wires to test.

https://www.2carpros.com/articles/how-to-check-wiring

If you have an open circuit the fans will come on. Check out the images (below). Please let us know what happens.
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Wednesday, February 12th, 2025 AT 9:11 AM

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