SureTrack Community Fix: Reverse Air

Real Fixes from the SureTrack® expert information resource are documented issues from actual shop repair records and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is currently available free with the purchase of a current Snap-on® diagnostic software version or in our ShopKey Pro product.


It’s always frustrating when you replace a part and the new one doesn’t work as it should. SureTrack community member bmaples had a BMW X3 SUV in the shop where they replaced a bad HVAC blower and now it only had a little bit of air coming out of the vents. They posed the question to the community, and with the help of fellow community member Ericsautomotive and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2004 BMW X3 30i 3.0L

Title
Little air coming from vents, rewired blower motor.

Complaint
Customer complains that no air is coming from vents.

Diagnostic Steps Performed/Parts Replaced
Checked vehicle and confirmed that no air was coming from the vents when heater or air conditioner was on. Found defective blower motor. Replaced blower and now it’s working but very little air coming from the vents. Scanned with the Zeus and get code 20 for AUC stores. It appears none of the modes work except the fresh/recirc function. Have confirmed the doors for Fresh/Recirc work visually and can hear the pitch of the air sound change as well when fan speed is changed, Do not hear that when working the modes like Face and Defrost and very little air coming from face vents. The vent shut off knobs work and I can see the doors are open. A/C compressor engages and Lo aide line sweats and the little bit of air coming out feels cold. I read something in the limited service info BMW provided and it mentions something about and exhaust fume sensor can shut things off but no testing for codes or even a DTC index is provided. Is this code 20 the cause of my problems? Are there any tests available to help me further diagnose this? Any tips our guidance is greatly appreciated.

Best Answer from Community Member Ericsautomotive
Make sure the polarity of the blower motor isn’t backwards. It might be that the new motor is not wired correctly.

Cause
Checked the blower motor wiring and found that the polarity was backward as Ericsautomotive suggested.

Correction
Corrected polarity of blower motor wiring and it now turns the correct direction and air flow is restored to all vents as it should be.


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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.