Recover the refrigerant with a recovery/recycling/charging station.

Remove the relief valve cover (A), the relief valve (B), and the O-ring (C). Plug the opening to keep foreign matter from entering the system and the A/C compressor oil from running out.

Clean the mating surfaces.

Replace the O-ring with a new one at the relief valve, and apply a thin coat of refrigerant oil before installing it.

Remove the plug, and install and tighten the relief valve.

Charge the system.