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New guy. Fan question

rose62

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My wife has a totally stock '17 GT. I've recently noticed the a fan is running constantly. Looking at the owners manual, I removed relay #91 and it stopped. I metered the relay but I don't know what it should read. The large contact spades (the load, I assume) read open but the control contacts read .08 ohms. Is that normal?

As an aside, recently a piece of treadplate flew off a truck and wedged into the front bumper. The bumper and headlight were replaced. Could this have caused the problem? It began over a month after the repair.
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MikeHTally

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Do you run your A/C all the time? A fan will run if the air is running.
 
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rose62

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Do you run your A/C all the time? A fan will run if the air is running.
Humid Georgia, so generally, yes.

Edit: Just deactivated the climate system and the fan continued to run.

received_794064744634486.jpeg
 
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boB

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A typical 12V relay might read about 100 ohms across the coil. Some have a diode across the coil for suppression and that could throw off the ohm reading in one direction.
 
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rose62

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I just ohmed the relay and another that has the same schematic. They measured the same. I'm leaning toward the likelihood that the harness was damaged when the metal went through the bumper.
 

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Call_Me_Bruce

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I just ohmed the relay and another that has the same schematic. They measured the same. I'm leaning toward the likelihood that the harness was damaged when the metal went through the bumper.
You really need a bidirectional scanner to help troubleshoot. A bidirectional scanner can command the fans turn on or off. Typically the fans kick on with the AC running or when the coolant gets to about 210 F. A scanner without bidirectional control but with live data should be able to tell you coolant temperature. So with the AC off and the car from a cold start, no fans should be running. From what you are describing sounds like you have a dead short/harness damage. You can get a subscription to Alldata and pull a wiring diagram for the cooling fans and trace the harness to look for damage. If harness is good, try some swap-tronics and put a known good relay in and see if that helps. If relay is good, harness is good, connectors are good, then I'd lean towards problem with the fan itself.
 

EFI

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Was this bought new? It could have a tune from a previous owner that turns on the fans much sooner than stock settings to help keep the engine cooler. Alot of tuners do that.
 
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rose62

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Was this bought new? It could have a tune from a previous owner that turns on the fans much sooner than stock settings to help keep the engine cooler. Alot of tuners do that.
We bought it two years ago with 8k miles on it (it now has about 20k). The issue began within the last month.
 

PoCoBob

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Do you mean it never shuts off even when the car is off and it still never shuts off? I had that issue with my Edge a couple years ago. The Ford service guy told me that all relay's that look the same and have the same pin pattern are the same. So since you know it's #91 find another relay that is the same and move it to that spot and see if anything changes. If it does then it's the relay and they're pretty cheap to replace.
 
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rose62

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Do you mean it never shuts off even when the car is off and it still never shuts off? I had that issue with my Edge a couple years ago. The Ford service guy told me that all relay's that look the same and have the same pin pattern are the same. So since you know it's #91 find another relay that is the same and move it to that spot and see if anything changes. If it does then it's the relay and they're pretty cheap to replace.
If the engine is running the fan is on.
 

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if you have forscan, or know someone locally with it you can control the fans. If you command the low speed fan off and it doesn't shut off then there could be a relay problem. i use the high speed control when sitting in the pits between track sessions.

bcm.PNG
 

GreenS550

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I would get an obd scanner to see it if pulls any codes. Forscan will work, but why did it suddenly stay on is the question. It seems a sensor is bad telling the car it is running too hot I would guess.

Is the temp gauge in the normal range?
 

DansFLHTI

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Or you could remove the relay with the car off....start car and slowly install relay...see if you can feel the load contacts making...if you cant feel them making maybe the contacts are stuck together(relay is toast) try anther relay.if you can feel them making that is telling you there is 12v being applied to the trigger coil for some reason....or the ground side might be the switched side and it is switched on. The trigger voltage and ground are external to the relay.
 

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A fan running continously at high speed can also be an indication of a fault somewhere else (that is, not with the fan or relay themselves). Like an incorrect pressure in the A/C system, for instance. But in that case I would expect a DTC to be stored.
 
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Cory S

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Are you 100% positive you don't have any operation of Climate/AC/defrost active?
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