Blowers not working...ac or heat

So we had the AC fixed on our 99 blazer last summer and it was a God send! Until...it stopped working. To be more specific...there is cold air there, but it doesn't seem to want to come out of the vents! And then it does. So if you switch from the windshield defrost to the vents, to the AC and back...sometimes it will kick and blow and then after a short while, it stops again. This is the same with the heat, except now we haven't been able to get the "trick" to work anymore. The hot air will blow for a bit and then it stops. Even though you can feel the heat there. I live in Wisconsin...let me tell you, when I took the blazer to work on one of the coldest days this winter, I was NOT happy. My feet were frozen by the time I got to work...it was an hour and a half drive that day, of course!

We took it back in and they didn't seem to understand what the problem was or how to fix it. Is this electrical orr...I don't understand why it would work sometimes, and others not. More often lately its not. We seem to get more heat when everything is turned off. I would like to get this resolved before the summer temps are upon us.

Thanks!

To me it sounds like a lose connection somewhere or a bad ground. Seeing that it worked then quit. Could be the switch itself. Where the contacts in the switch isnt making a good conection. For me its hard to say what the exact problem is.

Automatic Climate Control or manual HVAC? Does the blower work on all speeds or is it an air distribution problem, (air flow does not come out where it's supposed to)? Can you vary the temperature of the air flow in the HEAT position?