Heat In 1996 Caprice Classic

Tell you what how you want for it obviously not much has problems so lmk know and I'll fix it in my garage hope that will solve the problem enjoy your day

It may have an issue with the HVAC control head or an actuator that controls the blend door. Get a competent mechanic to look at it for you.

Check the operation of the blend door actuator yourself. Cheap part and sometimes easy to find and replace. Most often behind the glove box top of the HVAC blower motor. Your vehicle may very well have a combined system that is both electrical and vacuum operated. So it could be a lost vacuum or actuator. Most likely a broken gear inside the actuator is my guess as the AC works fine.