When temp control fan is off, or on, there is hot air blowing through the floor vents, can I fix it cheaply?

There is a valve used to be on the firewall but could be in the interior, I had a gm car that run warm and I wanted to relieve the extra heat from the system at all times. I took this valve off and it would let heat in the floor vent but the a/c still came threw the vents and I could direct the air to the dash or defrost as you stated too but had no control over this heat in the floor. It routes this back to the engine and I do not remember its name I saw in a Haynes book and decided to remove it to see if it would help and when I did I found out that I could not stop the air in floor deal and placed it back and it went away but as mentioned before I needed to cool my motor down so I took it back off and it did work I just had a warm interior instead.