A/C light flashes?

[02SilveradoLS]

I just bought a 2004 silverado with the automatic dual climate control. I can't seem to get the a/c to stay on. The little snowflake on the dash just flashes and then shuts off. I'm trying to test all the features to make sure they work. It is winter where I am, so i'm wondering if it won't come on because of the outside temp. Thanks again

[91k4x4]

theres a sensor in one of the ac lines that looks for enough pressure in the a/c system. it flashes when you have low pressure and the a/c wont come on. i know obs trucks had a recall because of faulty sensors but you may just need to get the system recharged.