A/C Problems

I recently purchased a 2002 Sonata. the A/C was intemitting, but now quite. Have no power at compressor. All fuses good, relay fine. Put 12 v straight to compressor, it cools, but then builds excess head pressure then releases. Any thoughts thanks

I had the same problem with my 99 Sonata. I took it to Hyundai dealer who ran diagnostics and found a short in the A/C control head--you know, the part with the buttons and switches. They quoted me an estimate of $722. This was mostly for the part, not the labor. Apparently, the factory wants over $400 for the part. I bought it used online for $35. I haven't installed it yet, I just received it, but if Hyundai said that was the problem, I believe them. Everything else they diagnosed turned out to be the right solution. So, if I have it installed and something else turns out to be the problem, I'm assuming the dealer would have some liability for the incorrect diagnosis (that I did pay for). The part has a 90-day warranty as well. So, check it out with Hyundai; They don't charge too too much for the diagnosis (well under $100) and if you let them do the work, they deduct the diagnostic fee from the final bill.