I spent around 20 years working in car dealership service departments finding car problems and repairing them for the customer. I no longer do it for a living, but i keep my wifes and my old mb's percolating. This is at least the third time that this forum has saved me from tearing one of these cars apart as I searched for a problem.
Instead I searched the forum and found this post that was the answer to my wifes car problem. (The rocker switch was partially switched which is a problem that I remember finding long ago. Brain cell deterioration I guess.)
Thank you bjcsc and GA-W123 !!!