2018 Isuzu NQR A/C Refrigerant & Oil Capacity

Quick answer

• Refrigerant Type: R-134a
• Full System Charge: 22.9 oz (650 grams)
• PAG Oil Type: PAG 46
• PAG Oil Capacity: 4.41 oz (130 mL)
• Low-Side Service Port: On the accumulator/dryer, typically on the passenger side of the engine bay, a larger diameter port with a blue cap.
• High-Side Service Port: On the liquid line, usually between the condenser and the expansion valve, a smaller diameter port with a red cap.

Why R-1234yf matters (though not for your 2018 NQR)

While your 2018 Isuzu NQR uses R-134a refrigerant, it's important to understand the industry transition to R-1234yf, especially if you have other vehicles or are a shop owner. Starting around 2014, new vehicle models began transitioning to R-1234yf due to its significantly lower Global Warming Potential (GWP) compared to R-134a. This change was driven by environmental regulations aimed at reducing the climate impact of refrigerants.

R-1234yf is a more environmentally friendly option, but it comes with a higher cost per pound and requires specialized recovery and recharge equipment. Shops working with R-1234yf need dedicated recovery machines to prevent cross-contamination with R-134a. While this doesn't directly affect your 2018 NQR, it's a crucial development in automotive HVAC.

Recharge procedure

Recharging your Isuzu NQR's A/C system properly is critical for its performance and longevity. Always evacuate the system thoroughly before recharging. This removes air and moisture, which can cause significant damage to the A/C components and reduce cooling efficiency. Do not simply "top off" the system based on pressure readings.

Here's a high-level overview of the proper procedure:

1. Recover old refrigerant: If there's any refrigerant in the system, it must be safely recovered using an EPA-certified recovery machine.
2. Evacuate the system: Use a vacuum pump to pull a deep vacuum (at least 29.5 inHg or 750 mmHg) for at least 30-45 minutes to remove air and moisture. This step is crucial.
3. Check for leaks: After evacuation, close the manifold gauges and observe if the vacuum holds for at least 15-30 minutes. If it doesn't, you have a leak that needs to be repaired.
4. Add PAG oil (if necessary): If components were replaced or a significant leak occurred, the appropriate amount of new PAG 46 oil should be added.
5. Charge by weight: This is the most critical step. Using a calibrated charging machine, introduce the specified amount of R-134a refrigerant (22.9 oz / 650 grams) into the system by weight, not by pressure readings. Pressure can vary widely based on ambient temperature and humidity, leading to over- or undercharging.
6. Test system performance: Once charged, start the engine, turn on the A/C to max cold and maximum fan, and check vent temperatures to ensure proper operation.

Common A/C problems for this vehicle

Isuzu NQR trucks, like many commercial vehicles, can experience some common A/C issues due to their demanding use. While specific issues can vary, here are some typical problems:

• Compressor failures: These can occur from prolonged heavy use, over/undercharging, or contamination within the system. Symptoms include a lack of cold air, grinding noises, or the compressor not engaging.
• Condenser issues: The condenser, located at the front of the vehicle, is susceptible to damage from road debris. A clogged or damaged condenser restricts airflow and heat exchange, leading to poor cooling.
• Evaporator leaks: The evaporator, located inside the cabin, can develop leaks over time, leading to a gradual loss of refrigerant. Symptoms include reduced cooling and a sweet, musty odor in the cabin.
• Blend door actuator failures: While not a refrigerant issue, a faulty blend door actuator can prevent cold air from reaching the cabin, even if the A/C system is functioning correctly.

When to call a pro

Working with automotive air conditioning systems requires specialized knowledge, tools, and an EPA 609 certification for handling refrigerants. While some basic troubleshooting can be done, any work involving opening the refrigerant system should be left to a qualified professional. Improper handling can release refrigerants into the atmosphere, which is harmful to the environment and illegal. Furthermore, incorrect charging or component replacement can lead to costly damage to your A/C system.

For accurate diagnosis, safe refrigerant handling, and proper repairs, always consult an ASE-certified HVAC technician.

Safety Disclaimer: Automotive A/C systems contain refrigerants under pressure. Improper handling can cause personal injury, including frostbite, and damage to the environment. Only EPA 609 certified technicians should attempt A/C repairs or refrigerant handling.

Find a certified A/C shop on Repairius.