Hey everyone. I recently replaced the A/C on my 7.5 liter truck. New comp., new accumulator, new orifice tube, new oil and O-rings, and flushed the whole system.

Two questions. What is the proper amount of 134a refrigerant? And what happens if I put the orifice tube in upside down? I can't find info on either one.

I do have a professional set of gauges. I did run a vacuum on the system. It seems to be working but the low pressure is about 35-40 during the cycle at 50° ambient. And I think I put the orifice tube in upside down!

 

Cooling, Heating, Ventilation & A/C - Ford Truck Enthusiasts Forums You would probably better to ask on the page in this link, the guys there really know all that stuff.
There should be a sticker with the amount of freon under the hood. And I would be surprised if it works at all with the orifice tube reversed but not an expert.
Try the page in that link and good luck, might even get a lot of info scrolling through the posts.

 

Thanks Lazy K. It is cooling but it's only 40° ambient here today so it's hard to say what it will do when we get to 90°

 

Orifice tube should be inserted with the "tabs" at the top:



The proper charge should be 80% of the R-12 recommended value. That works out to be ~35 ounces of R-134a. Until the temperature rises to a reasonable value your pressure values and vent temperatures are going to be skewed.