A/C issues

I noticed when I start my truck and turn on the A/C initially it makes a grinding noise when it is turned up full blast. I was also driving to the bay area with the A/C on the other day. It started getting cooler, so I turned the A/C off and decided to leave the vent on. I noticed the vent was not blowing cool air and it was getting hotter in the cab. I turned the A/C back on and haze blew out of the vents. It didn't smell like the motor was burning or anything so I continued to drive it and kept the A/C on.

First off, has anyone noticed the vent blowing hot air when the A/C is not on? Is this a normal thing for the vent? I noticed my GMC truck blew colder air when the vent was on, but it seems like the heater is on when the vent is running in my Tacoma. Has anyone had any of the other problems with the motor making a grinding noise or the vent blowing haze through the vents? I had my A/C motor squeaking a few months after I got it and the dealership gave me grief for making them replace it under the warranty. I finally told them I would go to another dealership for my business and they dragged their feet and fixed it. I don't want to go in there again and waste time if it is no big deal. It seems to be working fine now, but I thought it shouldn't be doing that to begin with.