My mother in laws Grand Cherokee with AZC the other day the fan motor quit working. I did some research and found that the blower motor resistor plug was bad, not burnt like some I saw online but the box did show signs of it being hot cause the plastic around the probes was melted some. Ordered a new plug then the fan works fine after plugging it back in then I noticed that the passenger side only had ac and the other vents blew hot air. I also heard creaking noises behind the glove box. I did some google searches and found out the noise could be the blend doors and that you can do a test with ac and recirculation buttons to get a code(s). So today the ac works great but no hot air at all, I tried to get the codes and it did nothing. From what I've read that could be the ac heater control is bad but I'm not sure if I'm doing something right or not and I don't want to have buy part after part to get it fixed. Not sure what to do next...

blend doors are fairly easy to replace you might want to check the door motor first make sure it is working remove the motor behind the glove box see if you can move the blend door rod you may find it just spins around if so they need to be replaced hope this helps

I'm having a similar issue with my '01 Grand Cherokee Limited. The blower would sporadically kick off during mid use or decide to work fine out of the blue regardless being a/c or heat. I've come to the conclusion it's the blower relay due to the fact I had a passenger accidently kick up under the dash with his feet and the blower turned on. My first reaction was "wtf did you do!?".. then "Whatever you did, it worked!" However, whether it's working or not. The passenger side vents omitt no air at all. Am I looking at blend door AND blower relay?

Sounds like a blend door issue. The doors breaking is very common. You can pull the actuators off and watch them move. If they do, you can probably eliminate the control head. Just like what he said above, you can grab the post that sticks out and see if it just spins, it shouldn't. If it doesn't spin around, that doesn't mean the doors aren't broke though. There are two doors on each rod and only one could be broke.

Columbus, I don't think there is a relay under there. There is a blower motor resistor and the blower motor. The motors get seized and smacking them will free it up for a little bit and cause it to work. You likely need a blower motor.