1996 Mercedes Benz S420 Air Conditioning

Contrary to what they would like you to believe, it's not possible to know how much refrigerant is in a system by reading pressures.

There is only one way to know and that is to completely recover the system, hold it under vacuum for 30 minutes and charge it with the exact required weight of refrigerant and not using those death kits from the parts stores.

Only then can you look at the pressures and get any idea what is going on inside.

I understand. If the EC light is on and cannot be turned off, then the compressor is not running, is that correct? And if the compressor is not running, then the reading from my pressure gauge would not be accurate, and additionally, I would not be able to charge the system either, is that right?

Until the system is charged with the correct amount of refrigerant, you aren't going to know if you have a gas problem or an electrical problem. You also have a computer in the mix that will shut down the system under certain circumstances.

Ok. I understand there will be various codes flashed but that the system will reset also? What is the sequence to turn off the EC light and to view these trouble codes?