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 Vapor Pressure Table
The vapor pressure tables for every refrigerant is published in the literature for the refrigeration system technicians. This table makes it possible to determine the vapor pressure acting on the column of liquid in a vessel if the temperature of the vessel is known.
Each refrigerant has its own characteristic vapor pressure table which one can differentiate the refrigerants through their pressure and temperature measurement under a specific temperature range. Does not apply for differentiating between R1234yf and R134a, their pressures are too close. Refer to REFRIGERANT PRESSURE AND BOILING POINT .
The possibility of distinguishing only applies to clean refrigerant whose vapor pressure differs sufficiently. If different refrigerants are mixed with a new refrigerant (for example three different refrigerants to refrigerant R407C) a vapor pressure will occur that corresponds to the vapor pressure of the refrigerant and its portion in the mixture.
In terms of absolute pressure, "0 bar" (0 psi) corresponds to an absolute vacuum. Normal ambient pressure (positive pressure) corresponds to "1 bar" (14.5 psi) absolute pressure. "0 bar" (0 psi) pressure corresponds to an absolute pressure of one bar on most pressure gauges (indicated for example by "-1 bar" (-14.5 psi) below "0" (0 psi)).
Pressure is measured in different units: 1 MPa (mega Pascal) corresponds to 10 bar positive pressure (145 psi). 1 bar (14.5 psi) absolute pressure corresponds to 0 bar (0 psi) positive pressure and thus to the ambient pressure (atmospheric pressure).
The vapor pressure of both refrigerant R1234yf and R134a are very similar across a large temperature range for this reason no differentiation of the two refrigerants is possible. Refer to REFRIGERANT VAPOR PRESSURE TABLE and A/C System, General Information . Distinguishing is only possible by suitable sensors which can analyze the chemical characteristics of the refrigerant. Refer to REFRIGERANT R1234YF ANALYSIS .
| Temperature in°C (°F) | Pressure in Bar (psi) of R1234yf |
|---|---|
| -40 (-40°F) | -0.40 (-5.80 psi) |
| -30 (-22°F) | -0.01 (-0.15 psi) |
| -25 (-13°F) | 0.12 (1.74 psi) |
| -20 (-4°F) | 0.50 (7.25 psi) |
| -15 (5°F) | 0.83 (12.03 psi) |
| -10 (14°F) | 1.21 (17.55 psi) |
| -5 (23°F) | 1.65 (23.93 psi) |
| 0 (32°F) | 2.15 (31.18 psi) |
| 5 (41°F) | 2.72 (39.45 psi) |
| 10 (50°F) | 3.36 (48.73 psi) |
| 15 (59°F) | 4.09 (59.32 psi) |
| 20 (68°F) | 4.90 (71.06 psi) |
| 25 (77°F) | 5.81 (84.27 psi) |
| 30 (86°F) | 6.82 (98.92 psi) |
| 35 (95°F) | 7.93 (115.02 psi) |
| 40 (104°F) | 9.17 (133.00 psi) |
| 45 (113°F) | 10.52 (152.58 psi) |
| 50 (122°F) | 12.01 (174.19 psi) |
| 55 (131°F) | 13.64 (197.83 psi) |
| 60 (140°F) | 15.41 (233.50 psi) |
| 65 (149°F) | 17.35 (261.64 psi) |
| 70 (158°F) | 19.46 (282.24 psi) |
| 75 (167°F) | 21.75 (315.46 psi) |
| 80 (176°F) | 24.24 (351.57 psi) |
| 85 (185°F) | 26.94 (390.73 psi) |
| 90 (194°F) | 29.09 (421.92 psi) |
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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.