Not yet, could be sensors feeding into the Klima relay. Most likely it is the temperature sensor. The Klima relay unit gets a signal from this temperature sensor, it is actually a switch, when the car gets too hot, the switch closes and Klima relay cuts off the compressor. The easiest way to confirm this is to disconnect the cable at the sensor.
Now if your system is same as mine on 87 260E, then look at this thread, I have posted a long step by step method of checking a/c system at the Klima socket.
http://www.peachparts.com/shopforum/showthread.php?t=158591&page=5