I've seen a lost of post recommending the blue or red orifice tube for a 134 retrofit, and even when used with a parallel flow condenser. But for those that have gone the additional step of the sanden compressor, which orifice tube are you using? I saw one post https://www.thirdgen.org/forums/cool...e-systems.html saying they used the variable tube, but just curious the results of everyone else. I'm here in TX and it's currently > 100* outside, so while this is not my daily driver, I'm definitely wanting the coolest air I can get.

 

I run the 0.057" Ford orifice tube in my Express van. It has a parallel flow condenser and a Sanden SD7H15 compressor with dual 3,000 cfm 16" fans. Did not notice a cooling difference on the highway but around town and at idle the a/c is 10°F colder. Both the low and high side pressures decreased with the smaller orifice. I run R152A. It idles at 42°F out of both front and rear units despite a 25% underdriven crank pulley and gets down to 33°F out of the vents on the highway. Rear unit has a TXV rather than an orifice tube. It practically gets cold enough to hang meat in there and will make your fingers sore if you you have the vents pointed anywhere in the proximity of the steering wheel. My old G20 van used to get that cold as well with a parallel flow condenser and a GM A6 compressor. To get them that cold without freezing the evaporator into a solid chunk of ice was a challenge. But I discovered a method to do it reliably. I set the cycling switch to 15 psi to prevent the low side of the system from dipping into a vacuum, then added a thermal cycling switch in line with the pressure switch. The thermal switch has a capillary tube that gets hose clamped to the low side line entering the evaporator after the orifice tube and then it gets covered in dum dum. I attach the switch to the evaporator box with a couple self tapping plastic screws. It cycles the compressor off when the refrigerant entering the evaporator drops below 30.5°F. Switch I used came stock on a 1988 Cadillac Fleetwood RWD with a 307 and is still available new from Four Seasons and other suppliers along with the matching connector.