You don't, this vehicle has (ATC) automatic temperature control and by doing this you will burn up either the controller or the head assembly......
The AC low side port on a 1999 Cadillac DeVille is against the firewall. It is on the larger of the two hoses going to the AC compressor.
Low refrigerant? Blown fuse? Bad compressor?
Find the low side ac port on the 1999 DeVille and connect an ac gauge and freon tank. Start the engine, turn the ac on high, and open the freon valve. Let the freon flow until the gauge reads full.
Connect a freon gauge and freon can to the low side ac port. Start the engine and turn the ac on high. Open the valve to allow the freon to flow until the gauge reads full.
Connect a freon gauge and tank to the low side ac port of the 97 DeVille. With the engine running and the ac on high, open the freon valve. Shut the valve when the ac gauge reads full.
If you are looking for the place to put the freon, it is the port closest to the front of the grill.....Left hand side.
low on freon
Disconnect the battery, then connect the freon so that as much as possible will go in, then re-connect the battery and start the car with the ac on high until you get the proper amount of freon.
Probably low on freon.
Probably low on freon.
the effectiveness of the compressor will be low and the temperature at which the environment is cooled will reduce.
The compressor wont turn if the freon levels are too low! It has a cutoff so if the freon all escapes the system the compressor wont be damaged.