Heat and AC not blowing or is inconsistent

I have a 1987 Chevrolet Nova and it hasnt been driven for a couple days because of the holiday. When I drove it today, the AC or Heat on the car wasnt blowing out at all I would only a get very little flow when I had it on fresh instead of recirculate which was just from the air flowing through the car I assume. This has happened before and it will not work for a while and then it will work again like nothing is wrong. It confuses me. Could it be a bad or loose fuse that could be the reason or is it something more? It seems to happen more so after it rains but I doubt there is a correlation.