2025 Kenworth T680 A/C Refrigerant & PAG Oil Capacity Specs

As an ASE-certified HVAC technician, I know that keeping a commercial heavy-duty truck like the 2025 Kenworth T680 blowing ice-cold air is critical for driver comfort, safety, and compliance during long hauls. Because commercial trucks have complex HVAC systems—often featuring a primary cab system and a secondary sleeper system—getting the refrigerant and oil specifications exactly right is crucial.

Here is your comprehensive A/C reference guide for the 2025 Kenworth T680.

Disclaimer: Automotive refrigerant handling requires proper training. Under Section 609 of the Clean Air Act, any person repairing or servicing motor vehicle air conditioning (MVAC) systems for consideration must be EPA 609 certified. Always wear PPE and consult your OEM service manual.

Quick Answer: 2025 Kenworth T680 A/C Specs

• Refrigerant Type: R-134a is still the dominant refrigerant in the heavy-duty truck market for this model year, though the industry is actively preparing for heavy-duty R-1234yf transitions. Always verify by reading the under-hood EPA compliance label on the HVAC box or firewall.
• Full System Charge Capacity:
  • Day Cab (Single Evaporator): Typically 3.0 lbs (48 oz / 1360 grams).
  • Sleeper Cab (Dual Evaporators): Typically 4.0 lbs (64 oz / 1814 grams). Note: Values can vary based on sleeper size (e.g., 76-inch vs. 52-inch) and APU integration. Always trust the under-hood spec sticker first.
• PAG Oil Type: PAG 100 (or Sanden SP-15 / PAG 46, depending on the exact factory compressor option). Check the compressor data plate to be absolutely certain.
• PAG Oil Capacity: Approximately 8 to 10 oz (236 to 295 mL) for a complete system flush and overhaul, but add only the amount removed during standard component replacement.
• Service Port Locations: Located under the hood on the passenger side. The low-side port is typically on the larger diameter suction line near the HVAC receiver-drier/accumulator, and the high-side port is on the smaller diameter discharge line between the compressor and the condenser.

Why R-1234yf Matters

While the light-duty passenger vehicle market began aggressively transitioning from R-134a to R-1234yf in 2014 to meet environmental regulations, heavy-duty trucks like the Kenworth T680 have had a longer regulatory runway. However, the commercial transition is here.

If your specific fleet model or APU utilizes R-1234yf, you must be aware of a few things:

• Cost: R-1234yf is significantly more expensive per pound than R-134a.
• Environmental Impact: It boasts a Global Warming Potential (GWP) of less than 1, compared to R-134a’s 1,430.
• Equipment Requirements: R-1234yf requires specialized, spark-proof recovery and charging machines (SAE J2843 standard) because the refrigerant is classed as mildly flammable (A2L). The fittings are also completely different, meaning you cannot accidentally mix the two refrigerants.

Recharge Procedure

When servicing a Kenworth T680, especially a sleeper model, precision is everything. Do not attempt a "top-off" using pressure gauges alone.

1. Recover: Recover the existing refrigerant using an approved machine to measure what was in the system.
2. Evacuate: Pull a deep vacuum (minimum 500 microns) for at least 45 minutes. A large truck system with dual evaporators and long refrigerant lines holds a lot of moisture. The vacuum boils off this moisture and verifies system integrity.
3. Charge by Weight: Charge the exact factory-specified amount of refrigerant in ounces or grams. Using a scale or an automated A/C machine is the only way to ensure the system isn't undercharged (leading to poor cooling and compressor starvation) or overcharged (leading to dangerous high-head pressures and compressor failure).

Common A/C Problems for This Vehicle

Even on a brand-new generation truck like a 2025 Kenworth T680, operating environments take a toll on the HVAC system:

• Condenser Clogging and Damage: Mounted at the very front of the grille, the condenser is a magnet for road debris, bugs, and rock strikes. A clogged condenser will cause high-side pressures to spike, cutting system performance and potentially damaging the compressor.
• Sleeper Line Leaks: Models with sleepers have long refrigerant lines running from the engine bay to the rear sleeper HVAC unit. The constant vibration of the chassis can cause these aluminum lines or rubber hoses to chafe, leading to slow leaks.
• Compressor Wear: Due to high engine hours and constant idling (if not equipped with an APU), the A/C compressor clutch and internal components endure heavy wear, making preventative maintenance and proper oil balancing vital.
• Blower Motor Resistors & Cabin Filters: Clogged cabin air filters are a leading cause of frozen evaporators and burnt-out blower motors. Regularly replace the filters according to your fleet's PM schedule.

When to Call a Pro

A/C repair on commercial equipment is not a DIY job. If your truck is experiencing electrical faults, rapid cycling, or a massive catastrophic compressor failure (which requires full system flushing, dual expansion valve replacements, and a new receiver-drier), it is time to turn to the experts. Putting an improperly serviced truck back on the road risks a breakdown and severe driver fatigue.

Find a certified A/C shop on Repairius.