depending on how low it is, it is either the fan rubbing against the casing or the belt that turns the fan coming loose.
check a/c compressor and belt.
Loose or glazed fan belt?
check your belts they can be worn and need to be replaced or they just might be cold unless its everytime you start the car if that's the case the might need to be tightened your ac belt or fan belt could be bad.
Loose or worn belt(s).
Check for a slipping drive belt between encine crank pulley and AC compressor pulley.
You may need to adjust your belts, check the ac belt first.
More likely the bearings in your alternator wearing out. Get a new alternator.
you should check the belts. Sounds like one is a little loose and slipping. or the system may be over-charged
It sounds like the fan-belt is slipping.
a loose belt between an engine pully and your AC pump is causing the squealing noise a loose belt between an engine pully and your AC pump is causing the squealing noise oic, come to find out that a bolt broke off that holds the pully that was causing the belt the squeel. Also, they ended up just replacing the water pump, saying, while we are in here, you prolly need another water pump cause they tend to got out at 60,000 and up, which is what my cars miles is. Thanks.
Worn serpentine belt and/or belt tensioner.
A worn belt will cause a squealing noise. The squealing noise is caused when the belt slips. Tightening the belt will temporarily fix the problem.