To forum and Arthur: on 450sl 1977 no climate control manual only. As anticipated, system overcharged binding comp and causing aux fan to run, red arrow in sight glass. Solution. gauges show overpressure, evacuate, charge with 2 cans freon12 (I once picked up 15 cans for 75 cents each) only 1 left.cools fine, aux fan OFF except when a/c on for a while. Keeping fingers crossed I think red arrow in sight glass shows system overpressurized. Hope this helps someone. Regards, Abe G