GM-GMC: Chev 1/2 ton a/c, freon 12, dessicant

Question
I had a front end accident in my 1992 Chev Extendicab last year and when the insurance company wouldn't repair the a/c without replacing the R12, I chose to recharge it.  Now, the a/c light flashes briefly when the truck is started.  It goes out, but the a/c does not work.  If I try to use it, the flashing light comes back.  Help!

Answer
I suspect that your A/C system discharged as a result of the accident.  If so, you cannot simply recharge it.  Air and moisture would have gotten into the system.  Of the two, the moisture (humidity in the air) will contaminate the receiver-drier assembly and render it inoperative.  Moisture and Freon 12 combine to make an acid that will destroy system parts (that's the reason that the receiver-drier contains a dessicant).
The system needs to be depressurized, the receiver-drier needs to be replaced (along with any other parts that may have been damaged by the accident or subsequent recharge and operation), and the system recharged.