* Ambient temperature: Hotter temperatures will result in higher pressures.
* Refrigerant type: Different refrigerants have different pressure-temperature relationships. (R-134a is common in older models, but newer ones might use something else.)
* Engine speed: Pressure will change with engine RPM.
* System condition: Leaks, clogs, or a failing compressor will all affect pressure.
Instead of looking for a specific number, you should consult your Ram 2500's owner's manual or a reputable A/C service manual for the correct pressure charts. These charts will provide pressure ranges based on ambient temperature and other factors.
Trying to diagnose AC problems by only checking low-side pressure is unreliable and can be dangerous. Proper diagnosis requires specialized tools and knowledge. If your AC isn't working correctly, take it to a qualified automotive technician for service. They have the equipment (like gauges that measure both high and low side pressures simultaneously) and expertise to properly diagnose and repair the system.
