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Discussion Starter · #1 ·
I’m really hoping for some help here guys. I have a 2006 XC90 2.5T AWD, the vehicle runs great, even with 182k on it. But the one thing that is getting super annoying with all this hot weather is, if i run my AC/heat at ANY level for any amount of time and then get to my destination and turn the vehicle off, the fan will continue to run until it kills my battery completely.

I assume there is some interior fan or a fan that cycles air even when the car is off. I have no clue what to do, its currently 98 degrees Fahrenheit and no AC is a super bummer.

I havent run the AC in a few weeks and the car starts up every time perfectly, I can run my radio, heated seats, any other device that I can think of, just not my AC.

Is there someone that can help this poor sweating guy out?
 

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Are you saying the cabin fan runs, or the engine cooling fan? If it's the cabin fan, you might try setting the system to automatic. Not that it's supposed to work the way yours does, but, my fan will run in the aux position of the key unless it's in auto, so maybe that will get it to shut off for you. Otherwise you're going to have to look at what's going on with the data network...
 

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I can't remember the blower motor on heat or a/c ever continuing to run once the car is shut off, no matter what the settings.
 

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All I can say is if I want to listen to the radio, and the fan speed has been set manually, the fan runs with the key in the "Aux" position. If I press "Auto" it shuts off.
 

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Discussion Starter · #6 ·
Yes, sorry I should have been a little more descriptive. If I turn the knob for fan speed whether it’s A/C or heat, the cabin fan will continue to stay on even after I’ve turned the car off.

Which I understand that sometimes fans will run when a vehicle is off to circulate cabin air as necessary. My problem however is it will just constantly stay on until it drains the battery and I need to jump start the car.

Any other accessory, radio/cd, heated seats, any other switch works completely fine and won’t drain the battery it’s only when I run the A/C


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So, how do you get it to shut off? Or do you have to wait for the battery to die?

Try pushing the "auto" button before you shut it off.
 

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Discussion Starter · #8 ·
So, how do you get it to shut off? Or do you have to wait for the battery to die?

Try pushing the "auto" button before you shut it off.
At this point if I ran it I would have to wait for the battery to die in order for it to shut off. Or unhook the battery. It’s really strange, so I’ve been driving all summer with no ac at all. I’ll definitely try the auto feature


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Yes, sorry I should have been a little more descriptive. If I turn the knob for fan speed whether it’s A/C or heat, the cabin fan will continue to stay on even after I’ve turned the car off.
Sounds like this really has not much to do with AC or Heat and everything to do with your cabin fan.

With engine running:

-Press the Auto button with 74 degree range on both temp knobs and let us know if the fan blows. Try to move the temp knobs (both) slowly to full hot, pause, then slowly to full cold. Any dramatic changes to fan speed?

-Turn fan controller knob from far left to far right in steps (Auto button light will go out)- does the fan increase and decrease speed as a step function to align with your turning the fan knob? Any large "gaps" in speed increase or decrease?

Let us know.
 

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Discussion Starter · #10 ·
Sounds like this really has not much to do with AC or Heat and everything to do with your cabin fan.

With engine running:

-Press the Auto button with 74 degree range on both temp knobs and let us know if the fan blows. Try to move the temp knobs (both) slowly to full hot, pause, then slowly to full cold. Any dramatic changes to fan speed?

-Turn fan controller knob from far left to far right in steps (Auto button light will go out)- does the fan increase and decrease speed as a step function to align with your turning the fan knob? Any large "gaps" in speed increase or decrease?

Let us know.
Okay, back to report my findings haha. So I did everything that you instructed and the AC and the heat along with the fan speed all act accordingly (in auto and manual) it’s a smooth increase/decrease in speed with no large gaps in speed change.

BUT, the damn fan just continues like the energizer bunny until the battery is dead.

Side note: after running the AC today and the fan staying on, I unhooked the battery for a moment, thinking it would stop the fan (which it did) but I only unhooked it for a couple moments and once hooked back up the fan returned to still being on. I then unhooked it for 10-20 minutes and then the fan stayed off.

Is there a simple relay/resistor or something that could be the culprit. Most times there’s loads of info on forums and YouTube, but I’m coming up empty with this issue.


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Couple scenarios as I am aware, always on or off, or off and fast with lack of speed varability a good giveway but this may have been a good test for the CCM. That the cabin blower is running after the key had been removed is still suggestive of a controller in my mind if the description of the fault is accurate.

But first things first, if you don't have a manual for this vehicle, you won't be able to know the right fuses to pull which, at this point should make your next test a little easier to do. Find it here- https://volvo.custhelp.com/app/manuals/ownersmanualinfo/year/2006/model/XC90

Fuse for cabin fan is the 30A in position 1 on the left side of the dash, see page 167 for location.

If you have the blower/fan fuse location, maybe no more need to mess with the battery while you figure this issue out, just pull the fuse when you turn the vehicle off. But put back in before starting, it's a big fuse for a reason...

The blower runs at a variable speeds as directed by the CCM via a PWM signal that's sent to the fan controller which leverages 12 VDC from the CEM (30A fuse 1) to power the motor.

So let's try this test again only this time let's pull the fuse when it does what it does and leave the fuse removed for 5 minutes, then put everything back and drive and when it still runs do the test for 10 minutes, then try 15, no need for more than that. If the fan is back to working "normal" after you replace the fuse for anything less than 5-10 minutes, then you'll maybe want to get a new controller but since this is 2006 with 13+ years of blowing, you might consider a replacement controller plus fan since you need to rip the fan out a bit to do the replacement. After market is reasonable for this application, I have a Behr blower in the '05 for quite a few years now as one example.

There's a chance it's the CCM but a few suggestiong that if the speed increase/descrease works, that's usually a good sign.

Let's see where you are after the next checks.
 

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When it stays on, is it at the speed it was running at on auto, or does it always go to a particular speed? Does the knob affect it when it is running with the key out? (Not that knowing will necessarily help, but to catalog the level of weirdness...)
 

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Any weird electrical issue just begs for a VIDA analysis. The results VIDA can spit out are truly incredible. One error code that my VIDA frequently show is that the drivers seat control buttons had too long a time making contact. Another one I see every time I run VIDA is that the cabin air temp sensor is showing too high resistance or open circuit. I can see that the sensor in the cabin air intake port is broken through the little grill. Cabin air temp sensor is something that may relate to your issue? Don't know, but maybe have a look in there after GENTLY vacuuming the belly-button lint out of the port. I suspect that too strong an air flow from a bad-ass vacuum could damage the little thermistor. I have a thermistor ready to install sitting on my desk, and marvel at how fragile it appears to be.
 

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It sounds relay related whether sticking or still receiving a signal when it no longer should.
Maybe get yourself a copy of a wiring diagram, fan controller (4/31) is a semiconductor device. Low current PWM waveform from CCM is "amplified" in a manner of speaking within the controller to provide a high(er) current variable duty cycle 12V waveform to run the blower motor (6/28).

CCM cannot run the fan on it's own, it needs the 12V feed from CEM managed by the fan controller.
 

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Don't know, but maybe have a look in there after GENTLY vacuuming the belly-button lint out of the port. I suspect that too strong an air flow from a bad-ass vacuum could damage the little thermistor. I have a thermistor ready to install sitting on my desk, and marvel at how fragile it appears to be.
Thermistor gets broke because someone thinks that little white dot behind the grate is not supposed to be there. I was at least smart enough back in 2006 after repeatedly poking at it with a toothpick to have taken a step back once I realized the part was there for a reason. You can vacuum and blow air on that little grate ad nauseum, I've never heard about or seen the thermistor get compromised through no-touch cleaning.

If the thermistor is broken, the usual symptom is blowing hot or cold with nothing in between.

Fully agree that VIDA/DICE is always the best approach for investigating vehicle issues and concerns.
 
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