how much freon in a port installed ac system,107
 

I have a 280 sl 1985 I have installed 4, 12 ounce cans of 134 and I still have a milky sight glass, 160 over 35 and it cools pretty well, but not great. The car was built without ac The afternmarket system was installed in Houston. Most of these add on systems that I have seen only take 2 lbs not 4. I had the evaporator out though and it is huge so I expect it may have a larger capacity. But more than 48 ounces? Help anyone?

The standard system called for 2.2 pounds of R12. With the R134A it would be 2 pounds. Mine was converted to R134 with a new condenser installed and my pressures are 225/23. Vent temps are 45F. This is with approximately 32ozs of R134A. I would say that you have too much R134. How much oil is in the system? It should be about 8 oz total. If you replaced any one component, you should add about 2oz of new oil and 4oz for the compressor. Maybe one of the AC guys will be able to help more.


BD:)

thanks for reply bdbenz. This system was already converted to 134. I was dealing with a poorly cooling system which led me to change the drier which was partly restricted. I addded 4 ozs of pag oil because I had the condensor cleaned and I replaced the drier. As I said, the system cools ok,(left my thermometer in someones ac vent sometime in the past)
Your answer tells me I have too much freon in but it doesn't explain my low pressures. I quit working on cars (except my kids and my own) when 134 came out, so I don't know much about it, but I suspect the site glass should be clear. Do you agree? My next step, without someone stopping me, is to add freon until the site glass clears(watching the hi side pressures of course)

BMunse,

I'm not an expert but I've been reading quite a bit on A/C systems as of late...both here and on a Porsche forum.
From what I recall your pressures look like they're in an acceptable range. Also, every expert I've come in contact with says NOT to use the sight glass to gauge proper refrigerant levels....especially in a 134 (R12 -134 conversion) setup.

The best procedure I've come upon is to fill or "top off" with the minimum or recommended amount of refrigerant. Use a themometer to measure vent temp. Add refrigerant until temps start to lower.

Hope this helps.

RickM is correct when he states that you can not use the sight glass for a measurement of the level of charge. With R134A, the recommended level is 80 to 85% of the correct amount of R12. So, on a fully charged system you will see bubbles in the sight glass. The only way to get the correct charge is with the gages. The high side pressure should be approximately 2.2 times the ambient temperature outside. Your vent temps should be somewhere in the 40's. Otherwise you may have a bad expansion valve.


BD

Thank you bdbenz. I hadn't seen that 2.2 figure. That means I will need to add more freon as the temp when I had the 160 reading was in the mid to high 80's.
I long for the simplicity of r-12. But the $30 a can price puts it in the russian caviar class.:D