I'm helping a friend in his attempts to make the A/C in his '85 280 SL work. When we started, the system was dead empty, but the compressor casing was dry around the shaft seals and it ran quietly when pressure switch was bypassed briefly with the dash controls in A/C position. Found an obvious leak in the condenser, so we are replacing the condenser and drier with new parts. All of the dash controls work correctly. Once the new condenser and drier are in, we plan to evacuate the system thoroughly and charge it with R-12. (I am hoping to get away with not messing with the evaporator or expansion valve.) Is there anything else I should check or replace before we have it charged? Thanx in advance for any advice.