Where is the orifice tube located?

 

It's in the hard line between the evaporator and the condenser.

 

Thanks

 

Zackly...

Right at the evaporator.

Undo the fitting connecting the smaller line to the evap. It is a plastic thing jammed into the line going into the evap.

If you're retrofitting to R-134A, Get the Frod red/orange one. Ask for about a 96 Crown Vic one at the parts store. It happens to have an orifice size that matches the needs of a GM R-12 system filled with R-134A, better than any of the GM orifices designed for R-134A do. I have been told that the blue Frod one also works, don't know what to order to get that though, and I've never tried it so take it for what it's worth.

 

(GM) White 0.072
(Ford) Blue 0.067

Red 0.062
Orange 0.057
Green 0.052
Brown 0.047

The stock orifice in our cars was the white 72. Most people recommend going for the Ford blue 67. I would recommend the blue as a nice upgrade to pretty much anybody. As for the red 62? That really depends. If you spend a lot of time in rush hour gridlock, it's alright. If you spend most of your time on the highway, stick with the Ford blue 67.

Here's the deal with orifice sizes. The smaller the size, the better refrigerant flow you get at idle/slow traffic. But the smaller the size, the worse you get during highway speed driving. This is why a NYC cab driver would do well with a small orifice while a weekend highway cruiser in sparse traffic won't see the benefit. Running at highway speeds with the smaller orifice raises the high-side pressure and puts more drag on the compressor.

 

I run the Red in my 1997 Express with dual air. The factory .072 SUCKS even in the factory R134a application. This is what the Red will do at idle with R134a. Not quite as good as Propane/Butane or R152a but I am back with R134a at the moment. Even with R134a I barely run 220-250 psi of head pressure on a 105*F day. High side pressure stays pretty constant with temperature/rpm but suction side pressure drops with the smaller orifice.