Your unit has an adaptive defrost control. I can't read the picture very well but there is usually a way to force the defrost mode. The directions could be on that sticker that you posted. You can try this, or, just check the limiter for continuity tomorrow. If it is closed, then it is working.

If the unit acts up again, change out the computer control.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2