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Discussion Starter #1
I got home from town today and after about 45 mins my wife told me my truck was making a strange sound like a fan was blowing. I go check it out and sure enough I hear a fan noise coming from under the hood. I open the door and get in and air is blowing from my vents?!?!?

So apparently it just started going sometime between when I got home and when my wife noticed it. Anyone ever heard of this and what it might be? Very strange.
 

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A friend of mine's old Honda Accord did this. It ended up being a stuck relay for the blower motor. Might be something to check


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A friend of mine's old Honda Accord did this. It ended up being a stuck relay for the blower motor. Might be something to check


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How does one check that?? Lol. I got in and started the truck and then killed it and it went off and hasn't came back on yet.
 

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Might be normal afterblow function. It dries away any condensation water to prevent mold and bad smell from the AC.
 

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If the relay were stuck I would think that it would've come back on immediately and would run constantly. I'm not familiar with our trucks yet as I've only owned mine since December, but at this point I could agree with Swede. It might be normal.


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Really? How did I not know about this? Lol. I've been driving Titans for 12 years and this is the first time I've seen or heard of this. Lol
 

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Ive never heard of this either, but as trucks get more modern, i dont see it run off of a relay anymore, and more likely to just be run directly off of the BCM correct? Or am i thinking about this wrong?
 

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You would still run the fan off of a relay. The amp draw of the fan is probably too great to run directly off of the BCM. Check your owners manual, it should tell you which relay is for the fan.

That said, if the ignition is off, then the fan should be getting no power. So even if the contact on the relay stuck, there wold not be 12v to power it. It will be almost impossible to diagnose now that it is no longer doing it. Next time it does it with the ignition off, see if other things are getting power as well. That will help point you in the right direction. Last thing, your ignition was off and not left in the accessory position right?
 

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I think it's a faily common feature on newer vehicles although few owners are aware of it. My 2002 daily driver V70 has it and people ask about it every now and then on the internet forums, assuming something is wrong.

Typically the AC control unit does an afterblow sequence if these criteria is met:
* Vehicle has been running long enough before turned off.
* Ambient temperature is high enough.
* Battery voltage is sufficient.

My V70 does an 8 minute max fan speed run, 50 minutes after ignition off. I think authorized shops can turn this function on or off. Default setting may depend on where the vehicle is sold... different climate zones etc.
 

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Discussion Starter #10
You would still run the fan off of a relay. The amp draw of the fan is probably too great to run directly off of the BCM. Check your owners manual, it should tell you which relay is for the fan.

That said, if the ignition is off, then the fan should be getting no power. So even if the contact on the relay stuck, there wold not be 12v to power it. It will be almost impossible to diagnose now that it is no longer doing it. Next time it does it with the ignition off, see if other things are getting power as well. That will help point you in the right direction. Last thing, your ignition was off and not left in the accessory position right?
The ignition was turned all the way off and my keys were sitting on the counter in my house. Lol
 
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