I am having the exact same problem on my 124 1988 300E.Gauges show a good charge. I am just driving along and the A/C cuts out and blower keeps going. Cycle the ignition switch and it comes back on. Now as it gets hotter here in vegas the ignition switch trick has stopped working!!
This is not a luxury here...... I will be watching this post carefully to see how it goes. Meanwhile I will be on my way to pick a part to grab all the ac stuff I can out of there 124's since that klima relay is over $100 bucks.................John
