R134a Pressure Gauge Chart
This chart details how ambient temperature correlates with the system refrigerant charge pressure, and how it affects high and low side psi readings. It can be used for recharging refrigerant, or to diagnose an a/c system based on pressure readings from your gauges.
| Ambient Temperature (°F) | Low Side | High Side |
| 110° | 50-55 psi | 335-345 psi |
| 105° | 50-55 psi | 325-335 psi |
| 100° | 50-55 psi | 300-325 psi |
| 95° | 50-55 psi | 275-300 psi |
| 90° | 50-55 psi | 250-275 psi |
| 85° | 50-55 psi | 220-250 psi |
| 80° | 45-50 psi | 175-220 psi |
| 75° | 40-45 psi | 150-175 psi |
| 70° | 35-40 psi | 140-165 psi |
| 65° | 25-35 psi | 135-155 psi |
A/C System Pressure Troubleshooting
In conjunction with a set of high and low side gauges, this temperature and pressure relationship chart can be used to diagnose an a/c compressor that is not working:
Low Side and High Side Pressures are Low
• Refrigerant charge below manufacturer specification
• A/C compressor not engaged / variable displacement inoperable
• A/C compressor performance deteriorating
Low Side and High Side Pressures are High
• Refrigerant charge above manufacturer specification
• Condenser fan inoperable
• Condenser dirty / airflow obstruction
• Internal obstruction of condenser
Low Side Pressure Low, High Side Pressure High
• System restriction
Pressures at or Near Equal
• A/C compressor failing internally
• A/C compressor variable displacement function inoperable
• Expansion valve failure