I have a 1999 E320 with 98K mile and the other day while driving I reduced the fan speed so I could talk on the phone w/o much fan noise ( i do this a lot) and when i went back to hit "auto" to return the climate control back to normal I noticed the EC light on and it has stayed on.
I've never had an issue with the climate control and it was blowing the same cold air that it always has prior to this episode.
After reading about a tech bulletin from another poster (re: changing regrig. temp sensor before doing anything else), I was wondering if that problem was mainly related to new vehicles and wouldn't pertain to a 7 year old vehicle.
Any thoughts on on what my first steps should be that can help solve the problem in a cost effective manner? Check refrigerant? Get a diagnostic test? just go ahead and change the sensor?

What type of refrigerant does this model use?

Thanks.