Dealer just sent me this picture of my orifice tube. They have been diagnosing warm A/C and finally came across this.

I've never seen an orifice tube so I could use some advice. When I first started having A/C probs I had oil leaking from compressor so I bought new compressor and drier and had small local shop install. The proverbial "new guy" in the shop forgot to install the drier and I drove about 10 miles before I got the call to come back and get it put on.

I don't know A/C systems or orifice tubes but this looks to me like years of accumulated gunk, probably not the result of 10 miles w/o a drier. Any comments? I don't know what the dealer will charge to replace but the part is only $84 at Jagbits and I've heard they are pretty easy to put in?

 

taking a look at the picture, it looks like the "black stuff" is simply aluminum oxide. This will form over years of use. Granted, in a lot of cases it is due to getting water into the A/C system (can only occur during install or running the car for a long time with no freon in the system) and then the water is corroding the aluminum. This will lead to the small opening in the orifice tube to become blocked, preventing the freon from flowing properly. The only other way for the oxides to form is to improperly fill the freon system by not drawing a vacuum on the system following some major repair. Drawing a vacuum on the freon system is necessary following the opening of the system to 1) make sure the system is empty so you can fill with the proper amount of oil and freon, and 2) having oxygen in the system will lead to more rapid corrosion in the system along with reducing the efficiency of the system since the system is now pumping a mix of freon and air, so, less freon makes it to the cooling coils.

 

The main purpose is that moisture, which yes is corrosive chris, is that under a vacuum it boils off any moisture in the system. You cannot run without a drier, only the old 1 still in place

 

Just to update anyone interested in one of the ways A/C can go bad, it turns out the trash clogging the orifice tube is mostly metal shavings, presumably from my old compressor (RIP). I think one of the lessons I learned here is don't just replace the compressor and drier, but also replace the orifice tube at the same time - or at least inspect it and clean it. The shop that installed the replacement compressor claims to have flushed and cleaned the system, but that wasn't sufficient to clean that much trash from my orifice tube.

Now that I am a bit more educated on the system my comment about 10 miles w/o drier is obviously ignorant - the mistake they made is that they initially put the old drier back on instead of installing the new one.

The good news is that knowing what the orifice tube does and knowing it was plugged by trash thrown from a dying compressor explains all the symptoms I've seen, and gives me hope that replacing the orifice and a good flush and vacuum will finally yield cold air. Hopefully I didn't get too much trash circulated past the orifice.

 

Just a note to anyone thinking of buying an orifice tube. There is nothing to them but plastic mesh and a pipe. They only cost a few $ on ebay so do not spend the crazy amounts jag will charge.