hot and cold air at the same time

I am getting both hot and cold air out of my heater at the same time. I have a 99 Intrigue with the 3.8 and electronic heat control. I have checked the engine area (the heater hoses flushed, the block flushed, the thermostat checked and radiator flushed) all to no avail. At present, I have the glove box cover off and can't seem to find anything that resembles a motor to check. The plastic frame around the interior of the glove box will not come out, it has a rivet in it in one area. I can always drill that out if it would help, but so far, I can't find a reason. If someone can tell me more about figuring this thing out, please help. It is getting colder by the day here and my daughter wants her car back! Thanks. Joe

Just for kicks, disconnect the fuse for the hvac, it is also the one for the radio, so make sure you know the anti-theft code, because you'll have to reset it as well. I've had the problem on my '98 as well. Once you re-connect the fuse, you'll hear an actuator in the dash cycle. Once it has finished it's cycle, you should be good to go, at least for a while. I think it has something to do with the electronic controller, but i haven't had a problem since I reset mine. It doesn't take too long, just be sure that the car isn't running before you do it.

this was a fairly common problem with the A/C...passengers side ice cold and drivers side would be normal outside temperature.I assume its the same with the heat. I honestly have no idea how it is fixed but it had something to do with the passengers door & resetting it.
weird, i know but Ive read it many times....

I disconnected the negative battery cable and left it that way overnight. When I hooked it back up the next morning, the heater worked as normal. While sitting in the car, I moved the passenger control to cooler temp setting. It worked, but now it seems it will not go back to normal. I changed the setting back to center (neither hotter nor colder than driver setting) and it didn't seem to make a difference, it was still cooler than the driver's side. I did not let it run too long before I shut the car off, so maybe it will be ok. If not, I will either remove and replace the fuse or disconnect the battery cable again. At least she is getting heat now. If anyone else has any suggestions, feel free to share them. Thanks.