It sounds like we've got similar things going on - I can feel the air moving out of the vents. Without my cig bypass, I'd be SOL, but even then, the cig bypass is not a perfect workaround - it's risky and dangerous since the blower is pulling a lot of amps, and I don't want to leave it in permanently of course. Here's a summary of where I'm at.
* Blower sometimes cuts out all together. Little to no voltage at the red wire going into the blower control module.
* Wiggling a wire behind the fan speed switch turned it back on for a little bit, but this could have been a coincidence.
* No rhyme or reason when it cuts out. I'll be driving and it will just stop blowing. It will die for sometimes a few days, then magically start up again.
Possible fixes for me to try at this point (waiting on parts)
* Ign. Switch
* Add capacitor to blower ctrl. harness
* I also read somewhere to identify the ground wire going into the harness, and add a secondary ground right to the chassis. I have not tried this yet, and probably won't until the two up above prove incorrect. My thought is that if a ground was bad, it would never work, but right now it works for a while, then dies. I'm no electrical expert, either.
Things that didn't fix it for me:
* New fan speed/vent control/climate control switch
* New blower ctrl module
* New blower
* New blower ctrl module harness (5-plug which goes into the blower ctrl module itself)
My ignition switch isn't supposed to arrive until Monday, so I won't have any updates until then. And, even if it does show up, I don't necessarily want to replace it until the blower is inoperative again - I basically have to wait until it dies, apply a fix, and see if it fixes my issue after running it for a couple of weeks. I'll have the dash torn apart ready to throw it in when the time goes. Right now, when it does decide to work, it works perfectly fine for sometimes 3 or 4 days at a clip, then suddenly it will die again. I've been looking around online for other GM's besides Impalas having this issue, since the basic setup is found in other GM's. No one seems to have a good answer to this, the closest thing I could find is replacing the ignition switch, but who knows if that's going to do anything.