Thank you Jim, it was design for R12 and converted by the MB dealer to R134a. The evaporator was replaced a year ago along with the dryer. I was planning to replace the dryer, flush it and go back to R12. I will remove the dash because I want to put all the vaccum element and the heater back to work. I believe that the repair shop disconnected the heater because is not use in our tropical weather (Puerto Rico). I hope is not complicated to flush the system. I will wait for your advice.
Thank you again for your time>