When running my A/C it is very quiet, EXCEPT, when I put it on full blast it makes a very noticeable, much louder humming noise. It still blows cold, just makes lots of noise.

Is that common, or, an indication of something going bad that I need to address??

Thanks!
JamesDINAN (from bimmer days)
'97 4Runner SR5, 4X4, 5-Speed

 

simple thing to check is the blower fan. i had a whole gas reciept stuck in mine earlier this summer. made a horrible noise and i thought it was much more serious than a little piece of paper stuck in the fan.

 

team_gforce: Thanks for the info; I'll look into that definitely!

 

Just as an FYI an A/C has no levels of "on". It's either "on" or "off". It's the fan that regulates how much air flows over the evap coil. If it's quiet on low and loud on high it's likely that your motor bearing is worn and it starts to vibrate at higher speed.

 

Sounds like either the "squirrel cage" (blower motor) has some sort of debris as team gforce said such as leaves or paper. Or you may have lost the weight or is out of balance on the cage itself which will cause noises on high speed. If the blower has been replaced recently you may have had someone that didn't know what the weight was for and thought it was unnecessary and took it off. I've caught a few newbie techs doing that myself.

 

Thanks all for the input. I purchased this vehicle (1st Toyota) a few weeks ago. With its low mileage and everything else being original on it, I think it's safe to say the blower is original as well. I will look to cure or rule-out the easiest (leaves, paper, etc.).