2018 Peterbilt 579 A/C Refrigerant and Oil Specifications

Quick Answer: 2018 Peterbilt 579 A/C Specs

• Refrigerant Type: R-134a
• Refrigerant Charge: 4.25 lbs (68 oz, 1928 g) - For standard day cab and most sleeper configurations. Always verify the under-hood sticker.
• A/C Oil Type: PAG 46
• A/C Oil Capacity (Full System): 11.2 oz (330 mL)
• Low-Side Service Port Location: Near the A/C compressor, on the larger diameter line running from the firewall to the compressor.
• High-Side Service Port Location: On the smaller diameter line between the A/C compressor and the top of the condenser, which is mounted in front of the radiator.

Disclaimer: A/C service can be hazardous and is regulated by the EPA. Federal law requires anyone servicing a mobile A/C system to be certified under EPA Section 609. This guide is for informational purposes only. Always consult the OEM service manual and follow all safety precautions.

Why R-134a Persists in Heavy-Duty Trucks

While passenger vehicles began a federally mandated transition to the more environmentally friendly (but more expensive and flammable) R-1234yf refrigerant around 2014, the heavy-duty truck industry has been slower to adopt the new standard. For the 2018 model year, the Peterbilt 579 still uses the tried-and-true R-134a. This is good news for owners and independent shops, as R-134a is significantly less expensive and can be serviced with older, more common A/C recovery and recycling machines.

Servicing an R-1234yf system requires a dedicated machine that meets specific safety standards to prevent ignition and ensure purity, representing a major investment for service centers. Because your 2018 Model 579 uses R-134a, you avoid these higher costs and complexities for now.

A/C Recharge Procedure

A proper A/C recharge is not just about "topping off" the system. To ensure longevity and optimal performance, the charge level must be precise. This can only be achieved by measuring the refrigerant by weight.

1. Recovery: The first step is always to recover any existing refrigerant from the system using an EPA-approved recovery machine. This is required by law.
2. Evacuation: Once empty, the system must be placed under a deep vacuum for at least 30-45 minutes. This process boils off any moisture that may have contaminated the system. Moisture is the enemy of an A/C system, as it can freeze and block expansion valves or mix with refrigerant and oil to create corrosive acids.
3. Charge by Weight: The most critical step is recharging the system with the exact weight of refrigerant specified by the manufacturer. For a 2018 Peterbilt 579, this is typically 4.25 lbs (68 oz) of R-134a. Do not rely on pressure gauge readings to determine the charge; they are unreliable indicators affected by ambient temperature and humidity. The precise charge must be weighed in.
4. Add Oil: If the system was flushed or a major component like the compressor, condenser, or evaporator was replaced, you must add the correct amount of PAG 46 oil to replenish what was lost. An entire dry system takes 11.2 oz (330 mL).

Common A/C Problems: 2018 Peterbilt 579

• Compressor Failures: The A/C compressor lives a hard life. Clutch cycling issues or internal failures are common. If a compressor fails internally, it will contaminate the entire system with metallic debris, requiring a full system flush and replacement of the condenser and expansion valve.
• Condenser Damage: Located at the front of the truck, the condenser is susceptible to damage from road debris like rocks and birds. Even a small puncture will cause a complete loss of refrigerant.
• Bunk Evaporator Leaks: On sleeper models, leaks in the rear HVAC unit evaporator core are a frequent source of refrigerant loss. These can be difficult to diagnose as they are hidden within the bunk's climate control housing. An electronic leak detector is the best tool for sniffing out these elusive leaks.
• Blower Motor Resistor Failure: While not a refrigerant-related issue, a failed blower motor resistor is common and will result in the fan only working on the highest speed. It is located in the main HVAC box on the passenger side.

When to Call a Professional

While some DIY maintenance is possible, A/C system service is best left to certified professionals. You should call a pro if:

• Your system loses refrigerant and needs leak detection.
• The compressor has failed, requiring a full system flush.
• You do not have an EPA Section 609 certification and the proper recovery/recycling equipment.

An improper charge or the introduction of moisture can lead to costly component failures down the road. Using the right equipment and procedures is critical.

Need a certified and trustworthy heavy-duty A/C shop for your Peterbilt 579? Find a certified A/C shop on Repairius.