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BMW Heater Fan

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My 2006 BMW 530i’s heater fan sounds like it has a bad bearing. The noise is similar to that of a leaf hitting a fast moving blade. The noise is intermittent and seems to be worse when the weather is cold. The noise gets louder when I turn to the left and quieter when I turn to the right. When I turn the heater off and restart the noise is often gone.

Either the blower motor is failing, or the plastic squirrel cage fan is coming apart. Or both.

Tester

Or there is actually a small leaf or stick that got stuck there. These can slip past the inflow screening sometimes. The other symptoms though are more consistent with what Tester says, a motor or cage problem. In any event, the unit is going to have to come out for a visual inspection.

That was my thought too; the fan needs a visual inspection. What has me confused is the increase in the noise when I turn the steering wheel to the left and a decrease in noise when I turn it to the right. Any thoughts about that?

I think you’ve got enough evidence to show the fan is noisy and likely needs replacement. I get a “roaring” sound out of the fan in an '01 Sequoia. So far, when I change fan speed the roar goes away. I know it is going to get worse, but for now I’ll live with it.

These fans work hard, they are moving all the time. As soon as your turn the key on the fan starts up. Eventually all that use is going to wear the thing out.

@LH1950 … here’s my (ok, probably incorrect!) theory as to why the fan noise is different when you turn. The fan has rotational inertia – it acts like a little gyroscope – which means it wants to stay pointed in the same direction (if you are going North, the fan prefers you continue to go North). Because of this, when you turn the car, the fan doesn’t want to change orientations, so the turning of the car puts a sort of precessional force on the fan bearing. Left vs right difference could be due to more play in the bearing in one direction than the other. Or the free play in the bearing is allowing the blade to hit the cage in one direction, but not the other.

On airplanes or hi-tech stuff like the space shuttles this effect is used to advantage, for stability and for keeping the flight going in the right direction. But for your car’s fan, it’s doing no good for you at all. Sorry, the fan needs to be pulled. Likely you’ll find a worn/loose bearing.