The guys at Mac's Radiator and Air Conditioning Service separate the A/C lines going to the evaporator coil inside the evaporator case, which is under the dash. The bottom line is unbolted, while the top line is released with the properly-sized line-removal tool, as shown. In the case of our '88 LX convertible, the A/C system was already discharged, so we didn't have to discharge the R-12 Freon from the system. If your car's A/C works, have the system discharged before disconnecting these lines. It's also possible to do the job without discharging the A/C system, but it's more difficult to access the heater core because the case is not as easily separated from the firewall. Both schools of thought are valid; it's up to you or the person doing the job.