The 1999 Cadillac models have automatic air conditioning systems that require R134 refrigerant to keep them pumping out cold air. R134 begins as a gas, and -- after being pumped to a higher pressure -- condenses into a liquid that reduces heat before moving through an expansion valve where the pressure is significantly lowered. R134 is then pushed through the vents by the Cadillac's AC compressor and released into the air, absorbing heat from the ducts which help cool the air. The cold air users feel is the chemical reaction had by the R134 while moving through the Cadillac's heating ducts.
Assemble your kit by following the included instructions. This will most likely involve attaching the pressure gauge and hose to the can of refrigerant. Only do this right before you are ready to start the refilling process, as it punctures the seal on your can.
Calibrate your gauge based on the temperature of the area in which you are working. This will usually entail just rotating your gauge, but refer to your kit's manual for specific instructions.
Open your hood and locate your compressor. The compressor is located at the lower left side of the engine near the pulley that drives the belt.
Locate the low-pressure port connected to your compressor. The cap on the low-pressure port reads "L."
Wipe the port clean, if necessary, as any debris that gets in the system can lead to permanent damage.
Attach the hose from your kit to the low-pressure port, and lock it into place.
Turn on your vehicle and run your AC on high.
Turn your gauge counterclockwise to start filling up the refrigerant.
Monitor your gauge until you are in the green area, which means a sufficient amount.
Close off the gauge.
Turn off your vehicle.
Remove your hose and reattach the cap to your low-pressure port.
Turn on your vehicle and ensure that your AC is working properly.
