Aftermarket stereo install - no heater does not work

A couple days ago I had a local audio installer install a Kenwood KDC-BT645U Car Stereo. The stereo is working fine but the heater no longer works properly. The temperature control does not affect the temperature of the output air. The air is only luke-warm. Also the buttons that are supposed to control the volume of air seem to be "off". If put it on the lowest air-volume setting there is almost no air coming out of the vents. I am taking it back to the installer tomorrow. I am wondering if anyone has heard of this problem? I'd like to go to the installer with some intelligent questions. Thanks.