Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Refrigerant Circuit Pressures And Temperatures
- When performing work on refrigerant circuit, observe all generally applicable safety precautions and pressure vessel regulations.
The pressures and temperatures in the refrigerant circuit depend on the current operating conditions (such as engine RPM, coolant fan level 1, 2 or 3, engine temperature, A/C compressor on or off) as well as on the effects of outside influences (such as outside temperature, humidity, desired cooling output).
In vehicles with A/C compressor regulator valve -N280-, the pressure is modified on the low pressure side by the A/C compressor regulator valve.
For this reason, values indicated in the following table are valid only as reference points. They are attained at an engine speed of 1500 to 2000 RPM and an ambient temperature of 20° C (68 °F) after about 20 minutes.
The connections for the pressure gauge set intended for the pressure measurement are indicated on the vehicle specific refrigerant circuit. Refer to Diagnosis and Testing (vehicle-specific repair information).
At 20° C (68 °F) with the engine not running, the pressure in the refrigerant circuit is 4.7 bar. Refer to REFRIGERANT R134A VAPOR PRESSURE TABLE .
Pressure is measured in different units: 1 MPa (mega Pascal) corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute pressure corresponds to 0 bar positive pressure and thus to the ambient pressure (atmospheric pressure).
- Refrigerant Circuit with Expansion Valve, refer to REFRIGERANT CIRCUIT WITH EXPANSION VALVE, PRESSURES AND TEMPERATURES .
- Refrigerant Circuit with Restrictor and Reservoir, refer to REFRIGERANT CIRCUIT WITH RESTRICTOR AND RESERVOIR, PRESSURES AND TEMPERATURES .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.