Problem with 2004 Honda Odyssey Fan Blower

Just had our '04 Odyssey with 162K miles to the Honda dealer to have some maintenance work done. Had cabin filter replaced for first time. Out of the service area, I started the engine fine, turned on heat/a-c, adjusting fan speed to high. There’s a pronounced hummer noise coming from under the dash near the blower. It’s a constant hum, not something associated with some debris that may have been dislodged or floated down into the blower area. The “pitch” of the hum increases/decreases with the blower fan speed. Service personnel came out, to include the manager, and they exposed the area where the filter was replaced; nothing out of place or loose. Told me I could schedule another appointment to have them clean out the area inside where the filter and blower are located. Told them that service should be provided as a part of the filter replacement if it could be a concern. Although I’m not a car-savvy person, I’m thinking the problem is due to replacing the cabin filter: new filter, increased air flow (and there is a substantial increase of airflow out of the dash ducts) to the fan blower – which as been operated with a dirty filter for probably a lot of miles and it has “worn” just right, that the increase in airflow is causing the hum. Fan blower spinning faster causing the hum? I dunno. Thoughts/suggestions welcomed. Thank you.

The filter itself might be the source of the hum, they should just try a new one. The noise can be caused by airflow over paper, like when someone holds a piece of paper to their lips and blows on the edge of the paper. This could be a loose crease in the element or the spacing between two creases that is “just right” to make this noise.

Could also be the bearing in the fan motor. It’s happened to me, but not in my Odyssey.

As a 35 year Honda and Acura dealership technician, I can tell you this is only caused by 1 thing. The big clue here is that this only occurred after replacing the filter. When removing the old filter, there were leaves and debris on the inlet side. When the filter was removed some of this got into the blower motor. It only takes 1 or 2 leaves to throw it out of balance enough to create exactly the humming noise that you describe. I have dropped the blower motor many times to remove leaves and eliminate this noise. It surprises me that they didn’t just give it back to the tech for a quick fix. there should be no charge for this, it should have been caught and corrected before they returned it to you.

But seriously, 162k before you replaced the cabin filter? That thing must have been pretty nasty.

Thanks to each of you for your comments. Conoso, I’ll contact the dealership on your point. Hokiedad, you’re right.

I hope it’s just debris in the fan. A filter that was extremely dirty would cause undo strain the fan motor and could have burnt out its brushes.

It was debris. Dealer handled it at no-cost. I suggested to them that when they have a similar situation as mine (or maybe not quite so negligent as me) that they check for debris and clean as necessary without having the customer return for a second stab at completing the job. They said they’ve already added this to their “customer service procedures.” Thanks, again, to all for your comments and recommendations.

You can’t damage an electric motor that operates a fan from the lack of airflow. The opposite is true. Trying to pump too much air with an undersized fan/motor can damage the motor. This is called over-horse powering the motor or going outside it’s service factor.

When there’s no airflow to the fan the motor isn’t doing any work. One example of this is when you turn a shop vac on the motor rotates at a certain RPM because the fan is pumping air. Now if you block the hose you hear the motor speed up because the fan isn’t pumping any air so the motor isn’t doing any work.


I’m guessing it is pretty common to replace a cabin filter, then the air flow increase, and sucks some debris into the fan that couldn’t make it prior due to the deceased suction from the clogged filter. But it might not happen immediately after replacing the filter. It may take a few times of turning on the ventilation before a leaf makes it’s way to the fan. Sounds like the dealer handled this w/ aplomb though. No harm, no foul.

At every oil change, just as a matter of course, while the old oil drains into the catch pan, I shop vac the vents under the windshield to clear them of leaves and debris. I usually get quite a bit out of that area. Not enough for a compost pile, but a surprising amount of stuff lodges there over the course of a few months driving. Takes 2 or 3 minutes. My way of dealing with this problem.

OP should consider to schedule the shop to bring all the routine maintenance suggested in the owner’s manual up to date. Will minimize the chance of more expensive and time consuming aggravations down the line.