Behind the right headlight .
Replace air pump
The starter for a 1999 Saturn is on top of the transmission under the air filter box. Remove the filter box for easy access.
All sensors, air pump, and EGR
under the air box
Air Conditioning Vacuum Pump.
On the line right at the compressor.
The air pump or smog pump on a 99 GMC Jimmy is located right behind the bumper, below the radiator, and on the passenger side.
Right next to the windshield washer reservoir.
Posted a link under "Related Links" below
More than likely your heater core is plugged, and will need to be replaced
it comes on to balance the air ride system according to the weight inside.
Yes, like most modern vehicles, the serpentine belt runs the water pump, power steering, alternator and the air conditioning compressor.