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.
Pressure-Temperature Relationship
A refrigerant, when confined in an enclosed space, increases in pressure as the temperature increases. Conversely, if the temperature is lowered, the pressure also decreases.
Depending on temperature, a corresponding pressure will exist in such an enclosed space. For example, at 70°F (21.1°C) a gauge will indicate about 71.0 psi (5.0 kg/cm2 ). The R-134a PRESSURE- TEMPERATURE RELATIONSHIP table shows this relationship.
| Temperature °F (°C) | (1) psi (kg/cm2 ) | ||
|---|---|---|---|
| 20 (-6.7) | 18 (1.3) | ||
| 30 (-1.1) | 26 (1.8) | ||
| 40 (4.4) | 35 (2.5) | ||
| 50 (10.0) | 45 (3.2) | ||
| 60 (15.6) | 57 (4.0) | ||
| 70 (21.1) | 71 (5.0) | ||
| 80 (26.7) | 87 (6.1) | ||
| 90 (32.2) | 104 (7.3) | ||
| 100 (37.8) | 124 (8.7) | ||
| 110 (43.3) | 147 (10.3) | ||
| 120 (48.9) | 171 (12.0) | ||
| 130 (54.4) | 199 (14.0) | ||
| 140 (60.0) | 229 (16.1) | ||
| 150 (65.6) | 263 (18.5) | ||
| 160 (71.1) | 300 (21.1) | ||
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NO RELATED
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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.