My 1990 560SEL was converted to R134 by the previous owner - but only partially. It blows cold most of the time but quite often it doesn't blow cold. So the problem is intermittent. That is unacceptable because (as many of you well know) in So Cal the only time it cools off is at night during the winter. The days here are hot all year long. My current shop has not yet been able to pinpoint the problem although recently they replaced the AC control module but the symptoms seems to not have changed. They seem to be fixated on the remaining R12 plumbing yet they have not said that is cause. The cost to replace that plumbing is very costly. I'm not willing spend a lot of money to get no results. Does anyone know of a reputable shop near the San Perdo area?