Loud Humming noise with A/C on & Idling

[lmarcus]

My 99 Ford Explorer XLT's A/C makes a loud humming noise when the A/C is on and engine at idle. The air seems to stay fairly cold. It almost sounds like it is coming from the air filter. It seems like pressure is building up, but I am lost trying to figure it out.

[rivguy]

sounds like the boot in the iac has torn. this gives a hoot/hum noise from the air filter.

[lmarcus]

Thanks for the advise.