I bought a 1999 230 SLK about a month ago. Naturally, rain fell here almost every day for about three weeks. Today was my first opportunity to go for a long drive without rain. I drove it for about 300 miles in the sunshine and it was fantastic. However, I did experience something that was quite odd. I had the climate control switches for the passenger and the driver set at the middle of the white, or on the border between white and blue. The outside temperature was in the mid- to upper-70s and it was sunny, so the air conditioner was running. The top was on, windows up, traveling between 60 and 70 mph. The vents on the driver's side blew cool air for long periods of time (30-45 minutes or so), then for no apparent reason, suddenly started blowing very hot air. This was not the air conditioner shutting down and the vents simply blowing in warm air from the outside; rather, the air was hot and felt like the heater was going full blast. However, the air from the vents on the passenger's side did not fluctuate and stayed cool. I moved the temperature control for the driver's side up into the blue zone and after a few minutes the heat went off and the driver's side vents went back to blowing cool air. This happened to me four or five times over the course of several hours of driving today. I do not know what caused it to happen. Has this happened to others? Does anyone know the cause or how to fix it? It is not a huge problem, but it is an inconvenience and I want to know if it is a symptom of a bigger problem.