I've got the same problem with the SDL. However, it is even more bizarre.
In the economy mode, the system works as it should for about 20 minutes. Then, you can feel the clutch start to engage like the compressor is trying to come on, but will not fully engage. I usually just set it to the a/c mode at this point.

If I turn the system off and then put it back on economy, it will run properly, again, for between 10 and 20 minutes, and then the problem starts all over again.

This is really baffling because it would seem that the pushbutton unit could not act this way.

Any ideas?