I have 93 GT, 5.0, 5 Speed and I'm having a problem with the selector on the control panel. I can select floor, defrost,vent, or A/C and the air blowing out only comes out of the defrost vents and a little bit on the floor vents. Not sure what the problem could be. Please HELP!!!!!

 

I am moving to the 5.0L area...welcome to the forum!

 

Vacuum leak. On the driver side firewall, there is a vacuum tree with vacuum lines plugged into it. Follow the one that goes to the passenger side firewall. There you will find the check valve (a small disc shaped black plastic piece) with 3 lines plugged into it. Make sure there is not a vacuum leak anywhere in that tubing. If there is not, the check valve may be bad. From the check valve, there is a line going through the passenger inner fender to the vacuum reservoir. Make sure the line there is good (you can access the reservoir from under the inner fender above the tire. If the vacuum lines are good, the check valve or vacuum reservoir could be the culprit, but luckily they are both very inexpensive at a pull and pay yard ( I have never found them at the auto parts store, but maybe you will have better luck.)