So I have this 1999 Silverado 1500. I could not get it to hold Freon it would only last a couple of days then go flat. I took it to a shop and they evauated it and recharged with Freon oil and dye. And told me to come back when system quit cooling. Strange thing is it is still cooling down to 40 after 3 weeks ? I,m confused also can't be that lucky. Anyt one know why my ac started working again and not leak?And no it was not the fill ports checked them with soapy water.