A question for the A.C. experts....

[radcon]

I just installed a new Seltec compressor and filter/drier in my '80 SC. To be honest, I was quite amazed by how well the system cools now, even with no other mods beside removing the bowtie under the dash. I still have one question: after charging the system with R134, I checked the sight glass. I alternately see white frothy flow for a couple minutes followed by a few minutes of darkness in the sight glass that looks like liquid. What should I be seeing? Is my charge too much or not enough? Thanks for your help.

[911pcars]

The sight glass is only an approximation of the correct refrigerant volume. The best way is to connect pressure gauges to the system. If the system is cooling well now, you can have the system pressures checked by an A/C shop just to make sure, but don't add any refrigerant based solely on the sight glass. Too much refrigerant can damage the system and/or decrease cooling efficiency.

Manufacturers only supply a sight glass on new cars (if at all) as a gross indicator of what's inside.

Sherwood Lee
http://members.rennlist.org/911pcars

[ruf-porsche]

Since less refrigerant is used when you convert to 134a the sight glass is not a good indication of proper amount of refrigerant in the system. The best way to determine the correct amount of refrigerant in the system is like 911pcars stated in his post.

[smoak]

It is my understanding that the site glass in NOT used any longer after you switch over to R134a. Your system should now be filled by optimizing the lowest possible high side pressure with the lowest vent temp possible. Some numbers I have seen that worked well were low side gauge pressures were 30 to 32 psi. and the high side pressures about 200 to 210. Of course, this is all on a system by system basis and each car can be different based on equipment, hoses, leakage etc. The goal is to get a low vent temp with not too much pressure on the high side. Too little 134a and the compressor goes kaput. Good luck and have a professional do this for you unless you are really experienced.