My' 98 Deville went low on refrigerant so put in 3 cans of 134A last nite . It was cooling well but not up to usual. This morning it tells me my refrigerant in low again and has no cooling at all?? I don't know where to looks first. The compressor was replaced 2 years ago. Apparently the 134A leaked out last night. Where is the most "likely" place to start looking for my problem. I am a fair mechanic on easy stuff but I am stumped. Any ideas where I should start would be appreciated.