I am working on my mothers 02 c240 right now and recently her AC off/ Rest (similar to older EC buttons) light has come on and stayed on. It cannot be turned off. A/C does not blow cold, or even cool for that matter. I am aware that typically this indicates a low refrigerant level; however, from what i understand the ACC collects sensor information as well as stores trouble codes. My question is that is it possible to view sensor information as well as retrieve trouble codes without the use of an expensive scanner tool (similar to the method that can be used on older E class cars). I am going home tomorrow evening and would like to at least be able to point her in the direction of what to do before I head home. I have already attempted to add refrigerant, but it will not take any. Low side pressures were around 60lbs if i remember correctly, indicating to me that the compressor is not running and the system is at somewhat of a level of equalization. I would have checked the high side, but couldnt find the high side port.

any information you might be able to give me would be sincerely appreciated!