2020 GMC Sierra 1500 A/C Refrigerant Capacity, Oil Type & Recharge Specs

As an ASE-certified HVAC technician, I frequently service the newer generation of GM trucks. If you are dealing with warm air blowing from the vents of your 2020 GMC Sierra 1500, having the correct A/C specifications is the critical first step to a proper repair.

Below is the essential reference guide for the 2020 GMC Sierra 1500 A/C system, including capacities, oil specifications, and critical service procedures.

Disclaimer: Automotive refrigerant handling requires proper training and equipment. Under the Clean Air Act, Section 609, any technician servicing MVAC systems for compensation must be EPA 609 certified. Venting refrigerant into the atmosphere is illegal.

Quick Answer: 2020 GMC Sierra 1500 A/C Specs

• Refrigerant Type: R-1234yf (General Motors transitioned from R-134a to R-1234yf starting on some models in 2013/2014, and by 2020, all Sierra 1500s use R-1234yf).
• System Charge Capacity: 21.2 oz (600 grams). Note: Values can vary slightly depending on engine package and cab configuration. Always verify against the under-hood A/C specification decal.
• PAG Oil Type: PAG 46 (specifically R-1234yf compatible, often designated as ND-Oil 12 or equivalent).
• PAG Oil Capacity: Approximately 4.2 oz (125 mL) for a complete system flush/dry fill. (Add only the amount recovered during service if not replacing components).
• Service Port Locations:
  • Low-Side Port: Located on the passenger side of the engine bay, near the firewall on the larger diameter aluminum A/C line.
  • High-Side Port: Located toward the front passenger side of the engine bay, on the smaller diameter aluminum line near the air intake box/condenser.

Why R-1234yf Matters

If you are accustomed to working on older trucks, the 2020 Sierra’s use of R-1234yf requires a different approach. R-1234yf was mandated because it has a Global Warming Potential (GWP) of less than 1, compared to R-134a’s GWP of 1,430.

While it is much better for the environment, it is significantly more expensive per ounce than older refrigerants. Furthermore, R-1234yf is classed as mildly flammable (A2L). Because of this, it requires specialized, spark-free recovery and charging machines. You cannot use your old R-134a manifold gauges or recovery equipment on an R-1234yf system without risking cross-contamination and equipment damage.

Recharge Procedure: Weight, Not Pressure

When servicing the 2020 GMC Sierra 1500, precision is everything. Because modern A/C systems use smaller charge capacities, being off by just an ounce or two can severely impact cooling performance or damage the compressor.

1. Recover: Recover the existing refrigerant using a dedicated R-1234yf recovery machine.
2. Evacuate: Pull a deep vacuum (minimum 29 inHg) for at least 30-45 minutes to boil off any moisture in the system.
3. Leak Test: Turn off the vacuum pump and monitor the gauges for 10 minutes to ensure the system holds the vacuum.
4. Charge by Weight: Using a digital refrigerant scale, charge the system with exactly 21.2 oz (600g) of liquid R-1234yf into the high side (engine off), or as a gas into the low side (engine running).

Technician Tip: Never rely on the pressure gauges on "DIY recharge cans" from the auto parts store. System pressures fluctuate wildly based on ambient temperature and humidity. Charging by weight is the only approved method for R-1234yf systems.

Common A/C Problems for this Vehicle

While the 2020 Sierra is relatively new, the T1XX generation platform has shown a few recurring HVAC issues:

• Condenser Leaks: GM trucks have historically suffered from cracked welds on the A/C condenser. While improved in this generation, front-end rock strikes or micro-fractures at the upper mounting brackets can still cause slow leaks.
• Evaporator Temperature Sensor Failures: If the sensor fails, the compressor may short-cycle or run continuously until the evaporator freezes over, blocking airflow.
• Compressor Clutch Issues: Listen for a metallic rattling or a failure of the clutch to engage when the A/C is commanded on.

When to Call a Pro

Because R-1234yf is expensive and requires specialized machinery to safely recover and recharge, DIY A/C repair is no longer practical or cost-effective for most truck owners. If your A/C system is empty, you have a leak that must be diagnosed using UV dye or a specialized electronic sniffer. Replacing hard parts like the condenser, compressor, or evaporator requires professional flushing and evacuation.

Don't sweat out the summer or risk damaging your truck's expensive climate control system. Find a certified A/C shop on Repairius.