Actually... modern vehicles are quite laden with "orifice tubes"... but by far the most common reference is immediately
BEFORE the AIR-CONDITIONING SYSTEMS
EVAPORATOR core. It is considered the transition point from the
high pressure side to the
low pressure side (SUCTION (return to the compressor))... More commonly called the EXPANSION VALVE.
Arguably the SECOND most common failure point in automotive A/C next to the
MAIN-SHAFT SEAL of the compressor itself.
Take a look at the eBay link and you will see an array of familiar looking (expansion valve) housings & valve bodies you have seen over the years... Clean work surrounded by fresh seals... all properly tightened.
Don't waste your money if you haven't read the (pretty simple) procedures... Refrigerant can be quite dangerous if mishandled...!!
Likelihood of success is pretty good ...
the real (A/C SERVICE) tools are not cheap... but you can recapture ALL YOUR COSTS on your first couple of jobs.
I had ten reasons for learning A/C.. Ten cars and NO COMPETENT/HONEST air conditioning
SERVICE/REPAIR within a 200 mile radius
Hope this helps
Denso 475 4113