2020 Mercedes‑Benz Metris — A/C Refrigerant Capacity & PAG Oil Specs

Quick answer

• Refrigerant: Most 2020 Metris (W447, North America) use R‑134a. A few late‑production/market variants may use R‑1234yf—confirm on the under‑hood label.
• Full system charge: Front A/C only ≈ 22.9 oz (650 g) R‑134a. With rear A/C (SA code H12) ≈ 38.8 oz (1,100 g). Always verify the exact value on the vehicle label or in Mercedes WIS.
• PAG oil: PAG 46 (ND‑8 equivalent). Total system oil: front only ≈ 4.1 oz (120 mL); with rear A/C ≈ 6.8–7.1 oz (200–210 mL). Verify per component replacement and WIS.
• Service ports: Low‑side on the large suction line near the right‑side firewall area (often under a plastic cover). High‑side on the smaller discharge/liquid line near the condenser at the front right, behind the grille/radiator support.

Why R‑1234yf matters

• Cost and availability: R‑1234yf is significantly more expensive than R‑134a and is sold in tamper‑proof small cans or cylinders. Many 2020 vehicles transitioned to YF, but the Metris commonly retained R‑134a in North America through this model year—check the label first.
• EPA and equipment: Recover/recycle/recharge (RRR) machines are refrigerant‑specific. YF systems require SAE J2843‑compliant machines and YF‑rated couplers and hoses. You cannot legally mix YF and R‑134a.
• Environmental impact: R‑1234yf has a much lower global warming potential than R‑134a. If your Metris is a late‑build with YF, you must use YF and YF‑compatible PAG oil.

Recharge procedure (high‑level)

• Identify the refrigerant: Read the under‑hood label. If it specifies R‑134a, use only R‑134a. If it specifies R‑1234yf, use only YF and YF‑rated equipment.
• Recover first: Connect an appropriate RRR machine to the low and high ports and recover any remaining refrigerant. Venting to atmosphere is illegal.
• Evacuate: Pull a deep vacuum (typically 29 inHg) for 30–45 minutes, then close valves and verify the system holds vacuum for at least 5–10 minutes. A rise indicates a leak that must be repaired before charging.
• Charge by weight, not pressure: Weigh in the exact charge shown on the Metris under‑hood label (commonly ~650 g front only; ~1,100 g with rear A/C for R‑134a). Use a calibrated scale. Slight under/overcharge will hurt performance and compressor life.
• Oil management: Only add oil when components are replaced or when machine accounting dictates. Use PAG 46 (ND‑8) for R‑134a systems; for any YF variant use YF‑approved PAG 46. Follow Mercedes WIS for per‑component oil amounts (compressor, condenser, evaporator, lines).
• Final checks: Verify condenser/radiator fans engage, inspect for line chafe, confirm blend door operation, and record vent temps and pressures relative to ambient with doors open and A/C at max.

Common A/C problems for this vehicle

• Condenser damage/leaks: The Metris condenser sits low and is vulnerable to road debris; pinhole leaks are common. Look for oily residue and UV dye at the condenser face.
• Compressor control valve or clutch issues: Denso‑type compressors can develop control valve sticking, causing poor cooling at idle or fluctuating pressures. Electrical clutch or coil failures are less common but possible.
• Refrigerant line chafe/corrosion: Suction/discharge lines can rub at brackets. On vans with rear A/C, the long underbody lines can corrode or chafe at clamps, leading to slow leaks.
• Pressure/temperature sensor faults: A faulty A/C pressure transducer can command fan/compressor behavior that mimics low charge. Scan with XENTRY and review live data before condemning hardware.
• Evaporator core leaks: Less frequent, but dye or a hydrocarbon “sweet” odor from vents plus a slow loss of charge points to the evap. Requires dash removal.
• Cooling fan performance: Weak or failed fan(s) will raise head pressure, leading to warm air at idle but colder air on the highway. Check fan command vs. operation.

OEM service information

• Mercedes‑Benz WIS/ASRA and XENTRY are the authoritative sources for specifications, oil distribution per component, leak test procedures, and HVAC actuator calibration.
• Capacity differences: Front‑only vs. rear A/C (SA code H12) have different refrigerant and oil capacities. Always match the charge to the exact build.
• Labels: The under‑hood A/C label is the final authority for refrigerant type and charge amount for your specific VIN.

When to call a pro

• If the system will not hold vacuum, if pressures are abnormal after a correct charge, or if you suspect electrical/actuator faults, involve an HVAC‑equipped shop with Mercedes diagnostic tools (XENTRY) and an SAE‑compliant RRR machine.
• R‑1234yf systems require YF‑specific recovery equipment and training. Many general shops cannot service YF economically.

Safety and legal note: Servicing MVAC systems requires EPA Section 609 certification. Refrigerant recovery is mandatory—do not vent to atmosphere. Wear eye/hand protection, and keep ignition sources away from YF refrigerant.

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