Hi, this is my first post. I own a 2006 GX470 and for the past few months I've noticed on and off scratching noise while stopped and in motion. I'm attempting to upload a video. Any input is appreciated.

Sounds like the gears on servo motor that controls HVAC are skipping...try switching between RECIR and flow through and see if noise goes away with one of the settings...the flap and motor are right behind CD player

Thanks, I’ll try that!

^^^^
What he said.

I ran the diagnostics. It is flashing between a 21 and a 24. Just got done driving and the outside temp is 48 degrees.

Switched from recirc to flow-through and that did the trick. Thanks everyone.

The three codes that you listed are always going to be in the system when checking the car when there is not direct sunlight on the vehicle. 21 and 24 are for the front solar sensors 28 is for the rear solar sensor. If you are in direct sunlight and you're still getting those codes then there is an open or short in one of the solar sensors and that could cause the air-conditioning to work intermittently but would be extremely unlikely. It's possible you could be low on refrigerant or a pressure sensor switch could be starting to fail or the magnetic clutch itself would cause an issue if the light in the AC button for the display starts to flash. That would indicate a possible problem with the magnetic clutch or the speed sensor in the air-conditioning compressor.

next is replacement of the servomotor......we have an old saying in medicine....when you hear hoof beats behind you....it’s usually horses....Not zebras. A common repair...