What is the correct operating pressures for R134a refrigerant in a 2003 dodge ram truck air conditioner?

There isn't a single "correct" operating pressure for R134a in a 2003 Dodge Ram AC system. Pressure readings depend heavily on ambient temperature and the system's overall condition (including the amount of refrigerant). You need to consult a pressure-temperature chart specific to R134a. These charts show the correct pressure range for different ambient temperatures at both low-side (suction) and high-side (discharge) ports.

Do not rely on a single number. Using incorrect pressures can seriously damage your AC compressor.

Instead of looking for a single pressure, follow these steps:

1. Find an R134a pressure-temperature chart: These are readily available online or in automotive repair manuals. Many HVAC supply stores will also have them. Make sure the chart is specifically for R134a.

2. Check the ambient temperature: Use an outdoor thermometer to get the current air temperature.

3. Use a manifold gauge set: You'll need a manifold gauge set with low-side and high-side pressure gauges and hoses designed for R134a. These are available at auto parts stores.

4. Check pressures at the low and high-side ports: Connect the gauges to the low-side and high-side service ports on your AC system (usually near the compressor). Turn the AC on full blast. Note the pressures and compare them to the values on the pressure-temperature chart for the current ambient temperature.

5. Interpret the readings: The chart will give you acceptable pressure ranges. Pressures outside these ranges indicate a problem, such as low refrigerant, a leak, a malfunctioning compressor, or a clogged expansion valve/orifice tube.

If you're not comfortable with this procedure, it's strongly recommended to have a qualified automotive AC technician perform the diagnosis and any necessary repairs. Improper handling of refrigerant can be dangerous and damage your system.