Hello all,

I have a worrisome new issue with my interior AC fan that has stopped working with no air flow, out of the blue. No noises or smells preceded the problem, just no air flow. The panel lights and switches all seem to work and respond normally. I can also hear the air direction servos working behind the dash as I increase the fan speed switch. I ran the HVAC code scan cycle on my Durametric and it produced the attached fault code. I tried to Google the code and it came back with nothing of value.

U040100
Invalid Data Received From ECM/PCM "A" Factory Fault Code 33540

I did have the AC Control Unit recall completed back in February and am hoping my current issue is related and thus covered by a one-year warranty..

Any help will be appreciated!

Thanks.

2012 Base V6 Panamera
74,000 miles
Located in Honolulu

 

I'm afraid you didn't mention whether you checked fuses. On the left side of dash open the door then carefully pry open the panel on dash left side.
57 is AC fan
5 is AC front + rear
just in case check 24 but unlikely.

This is from my '13 manual so hopefully the same...

 

Thank you for asking and I should have included in my first post. I did check fuses 5 and 47 but not 24. I'm also going to check the part number listed on my recall invoice. I'm not sure that the "Blower Motor Resistor" is the same thing as "AC Control Unit". Hopefully so. I also recall some mention of a relay being added to the recall service? Resistor change looks simple and I have done this on other make vehicles.

This is the kind of problem that can cost you between $200 DIY (best case) or $1,500 or more from dealer (worst case).

 

FIXED! I thought I would check the fan motor in the process of elimination and applied 12V to the blower motor input terminals. There was no response from the fan but a surprising amount of heat in the temporary wiring. I then decoded to remove the fan and have look. After easy removal I noticed a leaf or stem debris impacting the fan blades. I removed that and worked the fan until it loosened up. After hooking it back to temp power, it ran like crazy. Re-installed the unit, buttoned all back up and it runs perfectly again.

I think this fan will be problem in the future as the fan showed signs of overheating from the jam. Took some effort to loosen it up. Could be a day, could be five years. All I know is that this episode would have cost me about $1,000 at my local dealer. A new blower unit is expensive but the replacement process is very easy..

Big relief!

 

Excellent result.
As a bit of preventative maintenance,
Check the plastic strainer is located properly next to the hood hinge - might have become dislodged and allowed debris down into the fan duct.

 

Great news! Thanks for sharing the solution! (I don't even know where this fan is. Car is still less than one year with us).
So regarding air flow the fan comes before the cabin air filter? Sounds like a horrible amount of debris got into it!
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So the fan was not working again after day 2. Pulled the fan out again and this time I opened up the bottom cover piece of the fan unit (where the electrical wiring attaches) that is held in place by a single torx screw. Removing this piece allows access to the bearing end of the motor shaft. Upon inspection I found more debris but more significantly, a rusty shaft end that was clearly causing resistance for the motor to spin freely. I applied some Liquid Wrench to the bearing and shaft and let it sit (sitting on the squirrel cage). After that soaked in for an hour or so, I applied a 3 in 1 oil and motor oil mix and let that soak in for an hour or so. Fan spun much easier after this and hooking it up to temporary power yielded a much faster spinning fan! Replaced everything again and the fan is back in action and running noticeable faster on max setting.

I apologize for not taking pictures but I was in the heat of the moment. When you Google "Panamera Blower Motor" there is a YouTube video on removing the fan that is very helpful. In my case I also needed to remove part of the lower air ducting (passenger footwell area) to provide access to the fan screws. Removal (especially now) is very easy except for the cramped working area.

It is clear is that moisture has been getting to the fan motor and settling on the lowest point, which is the shaft bearing I lubricated. Car is always garaged but now 8 years old. Moisture could be from condensation or entry from the exterior. Hard to believe I am the only one with this problem but I do live in humid Hawaii.

 

Someone mentioned one of the cowl covers (assuming with a mesh to allow air into the system) might be dislodged, I guess it could be anything in the pathway there by that matter?

Since it's under the windshield if it has been replaced I've had shody replacement cause all sorts of strange leaks and eventual damage on my old Mercedes W123?

Wondering if these might be possible in your mind...