2018 GMC Sierra 2500HD A/C Refrigerant and Oil Specs

Quick Answer: 2018 Sierra 2500HD A/C Specs

• Refrigerant Type: R-1234yf
• System Charge Amount: 21.16 oz (600g)
• PAG Oil Type: PAG 46
• Total System Oil Capacity: 5.1 oz (150mL) - Note: This is for a "dry" system. Only add oil as needed during component replacement.
• Low-Side Service Port Location: Near the firewall, on the larger diameter aluminum line leading to the accumulator.
• High-Side Service Port Location: In front of the passenger side fender, on the smaller diameter aluminum line coming off the A/C compressor.

Why R-1234yf Matters

Starting in the mid-2010s, automakers began transitioning from R-134a to the more environmentally friendly R-1234yf refrigerant. Your 2018 GMC Sierra 2500HD uses this newer R-1234yf. While it has a much lower Global Warming Potential (GWP), it comes with a few key differences for service:

• Cost: R-1234yf is significantly more expensive per pound than R-134a.
• Flammability: It is mildly flammable, which requires different handling procedures and service equipment.
• Service Equipment: Servicing R-1234yf systems requires a dedicated recovery and recharge machine that meets SAE J2843 standards. Cross-contamination with R-134a must be avoided, as it can damage the system and the service equipment.

A/C Recharge Procedure

Accurately recharging your truck's A/C system is critical for performance and longevity. This is not a task that can be done properly with a simple DIY "top-off" can from an auto parts store.

The correct procedure involves:

1. Recovery: All existing refrigerant must be recovered from the system using an EPA-approved machine.
2. Evacuation: The system is placed under a deep vacuum for at least 30-45 minutes. This boils off any moisture, which is the enemy of A/C systems, as it can freeze and cause blockages or mix with refrigerant to form corrosive acids.
3. Charging by Weight: The exact factory-specified charge of 21.16 oz (600g) is weighed and injected into the system. Charging by pressure is inaccurate and can lead to over or undercharging, both of which cause poor cooling and can damage the compressor.

Common A/C Problems for 2014-2019 GMC Sierra HD Trucks

While generally reliable, this generation of Sierra/Silverado HD trucks has a few known A/C weak points:

• Compressor Failure: The factory compressors can be prone to premature failure, sometimes internally, which sends debris throughout the entire system. When replacing a failed compressor, it is critical to flush the system and replace the condenser and accumulator to prevent the new compressor from failing.
• Condenser Leaks: Located at the front of the truck, the condenser is susceptible to damage from road debris. Leaks often occur in the thin aluminum tubes or where the lines connect.
• Evaporator Core Leaks: A leak in the evaporator core (located inside the dashboard) is less common but more labor-intensive to repair. Telltale signs include a musty smell from the vents or refrigerant dye visible at the HVAC drain tube under the truck.

When to Call a Pro

Due to the specific equipment required for R-1234yf and the precision needed for a proper recharge, A/C service on your 2018 Sierra is best left to a professional technician. If your system is not cooling, a certified shop can perform a leak test, diagnose failed components, and perform the proper recovery and recharge procedure.

EPA Safety Disclaimer: Handling refrigerants without proper certification is illegal and harmful to the environment. All service must be performed by an EPA Section 609 certified technician.

Find a certified A/C shop on Repairius.