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MKX03

My cooling fan wires have power and ground

Question

So my 08 MKX overheated, and after some quick research, the first thing I suspected was the fans. 
I unplugged each fan one by one and connected them  directly to the battery for 1 sec to see if  they would turn  - and both fans worked.

So today I decided I would connect both fans to a fuse with power and a toggle switch so that I can manually control the fans so I can still drive it until I get the parts (I live on a small island in the caribbean - parts take a while)

Here is the weird part...

With  the fans 
disconnected from the control module, I connected a wire to the +battery and tapped into the red wire for main fan - then with a test light checked for power on the red wire (there was) -
but there also was power on the black wire. So the red wire and black wire must be touching or something. And  if I ground the black wire to the battery and test with a test light, both red and black wires now seem to be grounds. So I then tried testing the other fan the same way and it also had the same problem. 

Can anyone explain what might be going on?
And I tested the fans again by connecting directly to the battery and they work but I am afraid to leave them connected longer as I am not sure what is going on...

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12 hours ago, MKX03 said:

So my 08 MKX overheated, and after some quick research, the first thing I suspected was the fans. 
I unplugged each fan one by one and connected them  directly to the battery for 1 sec to see if  they would turn  - and both fans worked.

So today I decided I would connect both fans to a fuse with power and a toggle switch so that I can manually control the fans so I can still drive it until I get the parts (I live on a small island in the caribbean - parts take a while)

Here is the weird part...

With  the fans 
disconnected from the control module, I connected a wire to the +battery and tapped into the red wire for main fan - then with a test light checked for power on the red wire (there was) -
but there also was power on the black wire. So the red wire and black wire must be touching or something. And  if I ground the black wire to the battery and test with a test light, both red and black wires now seem to be grounds. So I then tried testing the other fan the same way and it also had the same problem. 

Can anyone explain what might be going on?
And I tested the fans again by connecting directly to the battery and they work but I am afraid to leave them connected longer as I am not sure what is going on...

Without having a wire diagram it's hard to know what the vehicle circuit is, but on older vehicles I worked on the red fan wire would go to a relay that when the ignition was turned on would connect it to the positive side of the battery. The black fan wire would go to a temperature controlled relay that when the vehicle engine was hot enough it would then connect the black wire to the negative side of the battery. Both relays would have to be closed for the fan to work. 

 

When you connected the fan red wire directly to the battery positive terminal and then checked from the battery negative to the red wire at the fan the light will light, but it may also light at the black wire if the engine is not hot enough to connect that side to the negative battery terminal by the temperature relay, this is because the fan motor will have a low resistance.

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But again, this all happens while the fan wires are completely unplugged from the control module. 

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You said you connected the fans directly to the battery and they worked. That means that the fans are fine. The problem is either the black line is not getting back to the negative side of the battery or the red line is not getting back to the positive side of the battery. On the red line there will be a fuse or circuit breaker and a relay contact before it connects to the positive side of the battery, Check fuse/breaker and relay contact. On the black line it would connect to the temperature controller relay then go to the negative side of the battery, that could be bad.

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Yes,  I am pretty sure it is the temp control module. And parts are already on order .

What I was looking for was help figuring out  how to temporarily hook up the fans so I can keep driving this thing until the parts arrive in about 2 - 3 weeks.

After digging a little more research, it seems there are no switches inside the cabin that can handle this type of circuit.

From what I see, the fans each need a 30 amp fuse and a relay + one 30/40 amp toggle switch to turn it on and off.
I was hoping there was an easier way to get the fans to work
 

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One quick test you could try is by putting the a/c in the MAX position and see if the fans operate (by-passes the FCV command signal from the PCM). As you only need the fans when idling or at very slow speeds (not needed at speeds above 20 mph) you may be able to switch the fans just on when needed.

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Yes I tried this already. Unfortunately the fans do not work with A/C on either

Edited by MKX03

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