Pontiac Repair: service engine light and a/c repair, pontiac grand am, giant hole

Question
I have a 2000 pontiac grand am se 4 cylinder I have 82,112 miles on this car my questions are:
My service engine light is on but whenever I fill the tank up it goes off but comes on again at a third of a tank full goes off at a half a tank and back on again at a quater of a tank.  I have been told at the dealership that the injectors need cleaning but wouldn't the warning light stay on if that was the problem?  My next question is about the a/c system last summer I had two pound of gas put in but it only lasted two weeks I returned to the dealership had more gas put in and a dye to detect a leak my problem no leak detected and the compressor is working what could the problem be?  The dealership repairs are eating a giant hole in my pocket are am I stuck with a money pit for a vehicle?

Answer
Hi, the service engine light this is a new one on me i have not came cross this type of problem, it could be a pressure sensor at the fuel tank. On the A/C if it is out of gas every time you have taking it to this dealer, then there is a leak some where. I would take it back to them make them fix it at there cost.