To find it, I recommend:
1. Consult your owner's manual: This is the best resource. It may have a diagram showing the location of various components, including the AC low pressure switch.
2. Use a wiring diagram: A wiring diagram for your specific year, make, and model will pinpoint the switch's location. You can often find these online through automotive repair websites or forums.
3. Visual inspection: Carefully examine the AC lines near the compressor. Look for a small switch connected to one of the lines, often with a single wire connector. Be cautious when working around the engine compartment; components can be hot.
4. Online forums: Search online forums specific to Dodge Ram 3500 trucks. Other owners may have posted pictures or descriptions of their switch's location.
Important Note: If you're not comfortable working on your vehicle's AC system, it's best to have a qualified mechanic locate and inspect the switch. Improper handling of AC components can lead to injury or further damage.