The condenser is located in front of the radiator and has become the most crucial part of the system since the switch to R-134A. Its major function is to condense the vapor to a liquid. Since R-12 changes states at a lower pressure than R-134A, the condensers used 40 years ago aren't as efficient as the condensers used today. So if you are piecing together an A/C system, you'd be better off not using anything designed before 1993 (the year the government mandated R-134A). Factory-installed condensers were often painted black for aesthetic reasons, but the paint can decrease efficiency.