Restoring Cold Air in the Miata

Spring arrived early in Raleigh, so fixing the barely-there AC shot to the top of the to-do list. This entry documents the troubleshooting and the final recharge.

Diagnostic Flow

1. Checked static system pressure (45 psi) and spotted oily residue around the low-side Schrader valve.
2. Pulled a vacuum to confirm the leak path; the system bled down ~10 inHg over 10 minutes, pointing to the valve core.
3. Replaced the low-side valve core, then inspected the evaporator drain and condenser fins for blockages.

Refill Steps

• Ran the compressor with manifold gauges attached, targeting 26-28 psi on the low side at 75°F ambient.
• Added 16 oz of R-134a with a splash of fresh PAG oil, monitoring vent temps (stabilized at 42°F on recirculate).
• Buttoned up the cowl plastics and re-secured the undertray.

Photo Log