Ac/heater controller flashes, air won't blow cool. I can't control temp, chg module same results.

What is your question?

When turn truck on the Hvac control light steady, air cool. 5 mins Hvac starts to flash, air goes warm.. Can't stop flashing and no air. I chg hvac module twice, however was rebuilt. Most of system has been chg. No leak on the ground.. I can hear ac click once I press it. The max air kicks on as well. All buttons work except for the coldnto got slide light flashes and prevents from controlling the temperature. Sometimes ac will blow good until lights starts to flash.

What makes this problem better or worse?

It's steady flashes

How long has your 1993 GMC C1500 had this problem?

4 months