Where is orifice tube located on 2006 Dodge 2500 turbo diesel located?

On a 2006 Dodge 2500 with a turbo diesel (likely a Cummins), the orifice tube isn't present. Diesel engines don't use orifice tubes as part of their air conditioning system. Instead, they use a different type of metering device within the air conditioning system's expansion valve or a fixed restriction. The exact location of this metering device will depend on the specific AC compressor and system design. You'll need to consult a repair manual specific to your vehicle's year, make, model, and engine for the correct information.