It sounds to me that you have a blower problem. I wouldn't worry much about fault codes they always seem to accumulate, but I very seldom get any usefull info from AC fault codes.
There is much writen about diagnosing the blower control on a 140 car and it is actually very simple. Remove the large cover at the right to center of the area below the windshield (numerous large phillips screws). Dislodge the routing of some hoses at the middle and leave the vacuum lines attached. Fold the cover to the side. This is the way into the fresh air filter and is purposely easy. Below the filter is the blower and the circuitry. There is a black chunk about an inch square mounted on the blower (comes with new blower) that is the blower regulator. It regulates by varying the current flow on the ground side of the circuit. So there are two large current carrying wires attached. There is also a signal wire attached that carries a 1-6v signal telling the regulator what to do. Look at the circuit find the ground wire from the blower. Check the power to the blower and then jump the ground from the blower to ground bypassing the reg. If the motor works, you have a regulator or control circuit problem.
If the testing is done properly a current test should be done as a high current motor will take out the regulator in short order. This is especially important on the 140 as the regulator comes with the motor.
You might also refine you capability to find a MB technician. You are right, he is not a MB technician if he doesn't know how to manipulate the PBC. Personally, I wouldn't use fault codes to look at your problem, but I would use actual values. One of the actual values is the PBC's idea of what control voltage was sent to the blower regulator. That should be the same as what is found at the regulator and it should rise and fall as the blower wheel is turned from "min" to "max".
And if you decide that the control signal is bad due to the PBC go here: www.beckmanntechnologies.com