ac and heater problem

I have a 1991 Chevy k1500 and the ac light will flash on heater console when it does that have no heat or ac then if i take the battery cable of both will work for awhile then quit again Please help thank you

I had similar problem with my 92 k1500, the entire screen would flash on the heat/ac control and i would have to shut the truck off and turn it back on for it to work properly. I had replaced the factory stereo with an aftermarket and when i reconnected the harness to the heat a/c control, i didnt get it locked in all the way and it was playing all kind tricks with the heat/ac control. i would check for good connection at the harness first and if that didnt work, consider replacing the unit.