Blower Fan(Defroster) Keeps Blowing - 2008 S80 T6

[Lukieb]

Hi all,

I'm hoping someone can help me with this problem. The symptoms is that randomly my internal blower fan decided to continually run if the battery is connected. I've done a lot of research, contacted a family member at the dealership and changed out parts to no avail at this stage.

More details:

Temporary Fix: Removed 40AMP fuse located under core fuse block in hood. This is starting to not be a great thing as the weather changes.

Troubleshooting/Fixes done:
-Replaced Blower Motor Resistor with genuine Volvo part(was replaced a yr ago by another mechanic with a lesser part)
-Replaced Blower Motor itself(What a PITA!)
-Tested a used CCM module. Same problem existed , but it was one revision different then what I had and some functionality stopped working so I pit back in the original.

I'm confused on what would cause this as I've read about afterblow and dont recall this ever being on before. I also have read that it shouldn't be enabled in my car regardless. What am I missing that could cause my blower to run? I'm just not quite sure what's telling it to run regardless of settings, and when the car is turned off with no key in the ignition.

Any suggestions would be helpful as I'm hitting a dead end and have already sank a few hundred.

Note: I have a family member who works at a Volvo dealership and their recommendation was to replace the two items i have. Im glad I didn't pay them beside I have to imagine that would have ran me a couple K.

Thank You.

[scot850]

How many miles on the car? It could be a worn ignition key that is leaving power to the BCU. Have you checked the BCU has not gotten wet? Not familiar with the location of this on the P3 S80. I know the XC60 one in in the Passenger side floor or just above.

Are the carpets wet at all? Need to check under them as they may be rubber backed.

Neil.

[Lukieb]

Appreciate your response. I'm not quite sure what the BCU is, but the car has had water under the floor mats previously due to leaks from the sunroof. If you're talking about the ECM then I had to detach all those wires and they're above the floorboard regardless.

Question about the worn ignition key. The key is removed from the car...if I unplug the battery and then reattach a few minutes later without the key; the blower comes on automatically.

Not sure if that clarification was required, but I do appreciate your response and anyone's willingness to provide some guidance.

[Lukieb]

Update:

Action #1: So I decided to remove the CCM from the equation(I think). I just removed its electrical harnesses.

Results: Blower keeps blowing.

So to the EWD and I would assume that the signal coming from the CCM would have to be consistent for the resistor to relay what to do with the fan speeds all else remaining equal. Although I will admit I have never looked at an EWD before or troubleshot this type of issue on a car before, so it's possible I'm missing something really basic.

Action #2: I decided to disconnect the resistor.

Result: Blower stops blowing.

I think I would expect this based upon the diagram where the blower motor receives its instruction from the fan control module(or resistor).

Overall: Could it be that I bought a resistor and/or the fan motor was having issues and therefore it blew my resistor? I'm still somewhat baffled, but hope someone would be kind enough to provide some help.

[Lukieb]

Closing the loop. I replaced the resistor again, but with a 30 dollar vs OEM. The problem is now resolved. I think I saw another mention of how the blower could blow the resistor. Maybe that's what happened? Either way, my recommendation if you run into a similar situation is to replace the blower and resistor.

[Lukieb]

And just to be specific. I would replace both before testing if it fixes your issue. You should also be prepared to grind a larger size socket you don't need to fit the size of the resistor 'handle'. This will help you not break your back as you twist and turn to get your hand onto it with enough leverage.

[paladin13]

I just went through the same thing with my s80, one thing to add to your results, change your cabin air filter as well. A new blower motor solves the issue of a worn out motor drawing more amperage and causing the resistor to blow, but a clogged filter will cause a new motor to draw more amperage as well and thus fry the resistor. If you haven't changed your filter recently, I would do so before you ruin another resistor

[Lukieb]

Yep. Did that at the same time. Might as well since it's in the same b@#$= spot