Confused about climate control

Well, to start with when I bought my car the previous owner said that the air conditioning only needed to be re-serviced, and I actually believed that. Anyway, I took it in today and the mechanic said that it still had freon, and that the problem was electrical. He hooked it up to a computer and said it was throwing a code for the sunload sensor. He couldn't get to it today because it would require the dash to come out, and he said even then he didn't know if that was the real problem. I did some research and found a climate control diagnostic test that Boone put on and I ran that on my car. In the sun it said 00 and in the shade it said 13. That means the sensor is working correctly right? Does anyone know? From what I understood that's how the numbers should read. Sorry this was sooo long, but any help would be appreciated. Thanks.