2020 Ram 3500 — A/C Refrigerant & PAG Oil Specs

Quick answer

• Refrigerant type: R-134a on most 2020 Ram 3500 trucks in North America; some late-production/market variants may use R-1234yf. Always confirm on the under‑hood A/C label.
• Full system charge: Most commonly about 24.0 oz (680 g) for R‑134a. Actual capacity can vary slightly by engine (6.4L Hemi vs. 6.7L Cummins) and supplier; always follow the exact charge shown on the vehicle label. If equipped with R‑1234yf, the published charge is typically in the same ballpark but must be taken from the label.
• PAG oil type/amount: PAG 46 (Mopar SP-20 equivalent) is most common; total system oil about 7.0 oz (207 mL). Component replacement oil quantities vary—refer to OEM procedures.
• Service port locations:
  • Low side: On the larger‑diameter suction line near the accumulator/evaporator outlet at the passenger‑side firewall.
  • High side: On the smaller liquid/discharge line near the condenser at the front passenger side (radiator support area).

Why R-1234yf matters

Starting in the mid‑2010s, automakers began transitioning from R‑134a to R‑1234yf to meet global warming potential (GWP) targets. While many light‑duty FCA vehicles adopted yf by 2017–2019, HD trucks like the Ram 3500 transitioned later. That’s why many 2020 Ram 3500 trucks still use R‑134a—yet some builds/markets can be yf. The under‑hood label is the final authority.

Key differences if your truck is R‑1234yf:

• Cost: R‑1234yf refrigerant is significantly more expensive than R‑134a.
• Equipment: Recovery/recharge requires a dedicated R‑1234yf machine with unique fittings and SAE J2843 compliance. R‑134a equipment cannot be used on yf systems.
• Serviceability: Shops must capture and recycle yf; adapters or mixing refrigerants is illegal and can damage the system.

Recharge procedure (high‑level)

• Verify the refrigerant on the under‑hood label and note the exact charge (oz/g) and oil spec.
• Inspect first: Check for obvious leaks (oily residue at hose crimps, condenser, compressor), condenser fin damage, and cooling fan operation. Do not “top off” a leaking system.
• Recover: Use certified equipment to fully recover any remaining refrigerant.
• Evacuate: Connect a micron‑capable vacuum pump and evacuate for 30–45 minutes. Verify the system holds vacuum (leak check) before charging.
• Charge by weight: Add the exact specified mass of refrigerant using a scale. Do not charge by pressure or “can feel.” Ambient conditions and variable‑displacement compressors make pressure‑based charging unreliable.
• Oil balancing: Only add PAG oil when components have been replaced or when OEM procedures call for it. Use PAG 46 (most common for this platform) and the correct quantity. Over‑oiling harms performance.
• Post‑checks: With A/C on MAX, doors open, blower high, verify clutch/commanded operation, condenser fan operation, vent temperature, and that high/low pressures track within expected ranges for ambient.

Important cautions:

• Never use sealers or stop‑leak; they contaminate equipment and can damage TXVs and compressors.
• R‑1234yf is mildly flammable (A2L). Avoid ignition sources and always use the correct machine, hoses, and fittings.
• Replace and torque service caps—these are part of the seal system.

Common A/C problems for this vehicle

• Condenser leaks/impact damage: The Ram HD condenser sits low and is exposed to road debris. Pinholes and fin damage are common.
• Compressor control valve or compressor wear: Variable‑displacement compressors can lose output due to control valve sticking or internal wear, causing warm air at idle and improved cooling only at cruise.
• Discharge hose/line leaks: Crimp joints at the compressor outlet can seep oil/refrigerant.
• Evaporator core leaks: While improved over prior generations, evaporator leakage is still reported—sweet odor/mist in vents, gradual performance loss.
• Airflow/temperature blend door actuator issues: Clicking actuators or doors stuck between positions can mimic A/C faults.
• Cooling fan or fan clutch performance (especially 6.7L Cummins): Weak airflow at idle raises head pressure and hurts cooling at a stop.
• Cabin filter/air path: 2019+ trucks may have a serviceable cabin filter; a clogged filter reduces evaporator airflow and cooling.

When to call a pro

• You suspect an R‑1234yf system (different service fittings) or don’t have SAE‑certified recovery equipment.
• The system won’t hold vacuum, indicating a leak you can’t pinpoint with UV dye or nitrogen/trace gas.
• Pressures are erratic, head pressure is high at idle, or vent temps won’t stabilize after a correct by‑weight charge—this points to airflow issues, a failing control valve/compressor, TXV restriction, or condenser inefficiency.
• Evaporator replacement is suspected—this is a dash‑out job best left to experienced technicians.

OEM service info notes

• Always follow the under‑hood A/C label for the exact refrigerant type and charge mass. Capacities can vary slightly by engine and supplier year‑to‑year.
• Mopar service procedures specify PAG 46 (SP‑20 equivalent) for most Ram HD R‑134a applications and a total oil fill near 7.0 oz (207 mL); component‑specific add amounts are detailed in the factory manual.
• Use the latest FCA/ Stellantis service bulletins for HVAC diagnostics and for any condenser or line supersessions.

Safety and legal disclaimer: Servicing mobile A/C requires EPA Section 609 certification in the U.S. Venting refrigerant is illegal. Use only SAE‑approved recovery/recycling equipment and follow all label and OEM instructions.

Find a certified A/C shop on Repairius.