I must have worked on Mercedes-Benz automobiles for 15 years before I ever replaced an evaporator. Through the 1970s, we pulled many an evaporator out of 107 and 116 chassis models to repair a poorly designed interior drainage system. The early models had little flappers on two interior tubes that carried the condensation to a lower tray that had the external drains. Originally, we were to open the case and snip the flapper from the end of the rubber tube.

Later, Mercedes-Benz came out with instructions and parts for the addition of two more external drains. The 114/115 chassis cars were equipped with heater motors that couldn't be removed without the removal of the evaporator case. The need for a heater blower now "totals" those cars.

Metallurgical changes were made in the mid-'80s, probably to save weight. Copper/brass were replaced with aluminum. Now, nearly 20 years later, evaporators are probably the #2 refrigeration problem, behind compressors. Though #2 in occurrence, evaporators are becoming a big #1 in cost.

Timely Work
Many manufacturers made provisions for easy removal of their evaporators, foreseeing replacement during the car's life. My experience with Mercedes-Benz says that they buried it because it would never need to be changed and then something went wrong. Two of its finest lines of the last 20 years, the 124 and 140 chassis, now come with footnotes about their cost of ownership due to air ...