I have 1990 300E/3.0. My AC was working fine. While driving in the morning, AC was on &cooling. In order to clear foggy windshield, by mistake I rotated the temp. dial to Max HEAT. Then, realizing my mistake, I pushed defrost button. After windshield cleared, I rotated the temp. dial to normal cold setting. The AC quit working. Blower is working, but I get only hot air.

Question: Could any body tell me sequence of troubleshooting this problem? Should I start with heater water valve? Is it also called monovalve? Is the valve located in front of battery?

Thanks