i have a 78 bronco that i am trying to get the a/c figured out before it gets hot here in michigan, right now it is 73 degrees out and my a/c is blowing air out of the vents at 66 degrees and the evaporater tempature is 57 degrees. the low side pressure is 21 pounds. it is factory air that i had converted to 134a. i replaced some hoses the drier and the condeser, ( i think that is what it is called, it is in front of the radiator). i have seen posts where it is recomended to change to orfice tube. i did not do that yet. is it necessary and does anyone have a 73-79 truck that has been coverted to 134a and how cold should i expect it to get.

 

I think you need to change your orfice and need to be much colder than 66 at the vent.

 

At that ambient temp. you should be getting 40-50°F. I don't think that system used an orofice- I believe that it uses a Thermostatic Expansion Valve (TXV)
What is the high side pressure?
mike

 

i dont have a gage for the high side pressure, i seen on ackits forum that the expansion valve works with both the r12 and the 134a. i am wondering if i don't have the correct amount of freon or the expansion valve is bad

 

Is there a chance that you have air in the system? Did you drav a vacuum on it before you filled it? Your symptom COULD be caused by low charge, but it could be something else too, and without the High side pressure we can only guess. Not a good idea to add more 134a w/o watching the High side- you could cause yourself grief.
BTW, do you know how much refrigerant is in there now?
mike

 

i had my friend fill the 134a, he is a certified mechanich and he pulled a vaccum before he filled it, i don't know how much is in there now since it may have leaked out but i dont think so, after he filled it, the ac never did get that cold and that was 3 years ago and now i am trying to figure it out so i can use it someday. what is the ideal high side and low side pressure, i will see about getting a gage a checking it, i would have my freind do it but he is in iraq SEMPER-FI