348 A/C converted to 134A need pressure spec..

One way to tell if the system is full is look at the sight glass on the filter/drier to see if it is clear with the system running. When it is clear, the High (pressure) side is pushing liquid through the drier-the system is full. When it is not clear, there will be a stream of bubbles flowing past the sight glass.
Since I don't have the ability to post a photo of what the hell I am talking about, perhaps someone can fill in for me.


Erik

 

True for R12, not true for R134.

 

Good to hear your air con is sorted out. As a rough rule of thumb, I try to get the temp at the vent to about 4 degrees celcius, that it with the thermo stat at full cold and the blower fan on the lowest speed to allow the air to absorb the coolness off the evaperator. As for the head pressures, I find if I run with between 10-18 PSI on the LOW and 180-240 PSI on the HIGH it's not a bad median for a cool vent temp. The rest is just trial and error

 

With r134, the lower the charge, the lower your temp (within reason).

This site says charge r134 to 90% of full r12 pressure for your vehicle (i.e. 10% less than R12): http://autoacrepairs.com/134aConversion.htm


This site lists an r134 pressure chart: http://www.ackits.com/index.cfm?fuseaction=Chart

Low Side PSI, Evap Temperature (F), High Side PSI, Ambient Temp (F)
16-29 , 33-50 , 115-200 , 70-80
19-39 , 33-60 , 140-235 , 80-90
25-43 , 40-65 , 165-270 , 90-100
37-51 , 48-65 , 210-310 , 100-110

 

absolutely.

You will not get rid of the bubbles in the sight glass in a system that has been converted from 12 to 134. Don't even try to keep loading 134 in an attempt to make them disappear.

 

"You will not get rid of the bubbles in the sight glass in a system that has been converted from 12 to 134. Don't even try to keep loading 134 in an attempt to make them disappear."


Whatever.

 

i would start with 70 percent of r-12 and work up from there . good info from the sckits site . if i can get the temperature coming oout of the vents 20 degrees lower then ouside temp i am happy . forza

 

I usually run at 30-33 Lbs and the vent temp is 40*F . My car sits all winter and when I get it ready for summer the system is at about 25# so I usually hit it with a small can of 134 until I get to 40#. Seems to work good in the 308. A little slow at getting the hot air out of the car but once I'm running it ie sufficent enough to keep me cool. Also a trick I use is turn the defroster vents so they are facing my head and that does the trick. Enjoy the ride

 

Look for a temperature differential of 18 to 22 degrees..........On a 90 degree day with a 90 degree temp inside the car, the vent temp will be about 68 degrees. You can do better with the old R12 systems......run at lower pressures

 

IN Phoenix in summer, that could mean 90 degree air from the A/C.

 

Speaking of which, could one have too much oil in a system, and what would that do.

I have a Porsche 928 coverted to R134a, and every time I check the pressure on the high side, I disconnect the guage and get a spray of oil.