This may be the silly question of the day, but I'll proceed anyway....

We bought our 2010 RX last December--dead of winter--and never noticed this until this week, when the temps are approaching summer, like upper 80s.

The AC (and heater) fan makes a loud droning noise (low frequency, but quite loud) when the "auto" setting turns the fan to one of the two highest settings to cool the car down. Never noticed this until now because the fan never ran at the higher settings in the winter (parked in a heated garage). It makes no difference which vent setting is used, the loud drone from the fan is the same as long as it is running at the higher speeds.

Also, I'm NOT talking about the fans in the seats. This is the big fan behind the dash. Manually decreasing the fan speed reduces the drone, which becomes almost inaudible at lower fan speeds. I searched and didn't find any similar threads/questions.

So, has anyone else noticed this type of fan drone noise?

 

There may be some type of trash/leaves in the blower motor. When is the last time the cabin filter was changed? Wouldn't hurt to pull it out and look. And see if there is anything in there.

 

[QUOTE=offroad200;8546853When is the last time the cabin filter was changed? [/QUOTE]

Cabin filter changed when we bought the car--like 6 months ago, and hasd only been driven 3-4K miles sine than. I'll go check anyway. Can't hurt.

 

Defintely check. Animals have been known to create nests in cabin filters. Or it could be something like leaves like offroad200 said. Just make sure it's on recirculate before you pull the filter.

 

And rats love to build nest in cars especially when people keep a food source (dog and cat food) in the garage. It's gross but it happens.

 

I try not to think about that. The RXh is parked near a brook and I've seen a few. Bird food is another attraction. They chewed a hole in the garage door to get at it. I keep a few boxes of 'blue pellets' around. Believe me I hate killing anything. I'm just trying to avoid any unpleasant surprises.

 

FOUND & FIXED!

Not a rat's nest.

Pulled out the cabin filter--clean as a whistle--looked new. Looked at the fan itself with a small flashlight & spotted some pinkish blobs that had adhered to the fan blades--very odd looking. Was able to scrunch my hand in through the filter hole and grabbed these blobs & pulled them out. Each blob slightly larger than a quarter, and appear to be some sort of insulation, similar to the blown-in stuff in most attics. Turned on the fan & it seemed quieter. There were two smaller dime-sized blobs that I couldn't grab, but I dislodged them & they (apparently) blew out into the duct work when I turned the fan on. No more visible blobs, so I reassembled everything and NO MORE DRONE. Sounds like a typical fan now.

OK, so what are these blobs and where did they come from? I haven't the foggiest idea, but I'm sure happy the noise is gone--restores my faith in Lexus. The blobs either were mistakenly "added" during manufacturing, or by some previous owner/garage when changing the cabin filter. Odd that such a small thing can create/cause such a big noise. BTW- that fan is relatively small, maybe 6" diameter, & turns at a very high RPM when on the high setting.

Also, no pets--no food in the garage--no rats either. A few small field mice in the vicinity (outside), but I'm constantly trapping these to reduce the population.

Thanks for the help guys!

 

Honestly sounds like something was starting to build a nest. I hope not for your sake but I've seen that before. In one car there was house insulation along with a pecan.

 

Sorry, I'm not trying to gross you out. Haha. Glad you found the issue and fixed it.

 

It would take MUCH more than that to gross me out. Anyway, there was no other material to be seen, such as mouse feces, fur, grass, etc.

Just those blobs of insulation. Pretty sure the blobs didn't get introduced since we have owned the car.

Now it's time to wait & see....

 

I'm leaning toward some animal building a nest in there too. Maybe the blobs of insulation were from inside the dash or firewall. I'd check the engine for more debris or chewed wires. Also spray a few short bursts of Lysol into the windshield cowl vents with the RX on and vents set on fresh air. Or use a vent cleaner just to be on the safe side. Those are available from the dealer or online. Maybe it happened before you bought the RX. Call the dealer to see if they've seen it happen before. Good luck.