Where exactly is the orifice tube located on my '91 F150? I've seen a parts diagram that appeared to put it in the inlet tube of the evaporator, but with the hose disconnected from the tube I see nothing. I will also mention that a recent episode resulted in the hose blowing out of the tube under pressure, which makes me wonder if the orifice tube may have been launched as well. Also, which tube would be correct when converting to R134? I've heard of red, blue and orange so far.

Any input appreciated!!

 

It certainly could have launched out under pressure. Actually that would be a blessing as most of them things are a real bugger to get out of the older F150 because the oring seize to the metal and they are deep down in the tube. You need a lot of patience to get it out when that happens often having to chip it out piece by piece with a pair of hemostat pliers.

A Red orifice tube is the most common and would probably work fine. You could also check with a parts store for the correct one for a 1994-1996 model which used R134 from the factory.