Ok so I'm trying to fix my girlfriends AC system before we both leave for college. I thought it was simply low or had no 134a in the system. I pulled a vacuum to find any leaks, turns out the system was sealed. So leaks are not the problem. I went to recharge the system to 1.5lbs and it was blowing cold for once! Then 2 minutes later, it warms up like there was nothing in it. I noticed that the high side spiked to like, 600psi and the compressor would not disengage. Thinking it was the high pressure switch I replaced that and the compressor is still engaged with the switch on. Am I missing something in the system? Could it be something as simple as a relay?