Hot air blows even on cold vent setting
 

I have a 1994 Honda Civic EX. Hot air blows through the vents at all times, even on a cool day. The only thing I can do is turn the fan to lowest setting and keep the windows down. It's as if a hot air damper is stuck open. Any suggestions?

There is a heater control valve on the firewall. When the lever is set to full cold, the push-pull cable is supposed to move this valve to the closed position and cut off the flow of hot coolant to the heater core.

Actually there are two cables involved. The first one goes from the dash lever to a mechanism on the bottom of the heater box. You can see this mechanism if you crawl in the floor from the driver's side. It's right in the center of the car. The mechanism moves a rod which operates the air door, and also operates the other cable which goes through the firewall to the water valve.

If nothing is completely broken, you may just need to adjust the second cable. Put the lever on hot and note that the cable at the valve is retracted, opening the valve. Then put it on cold and the cable should extend. Then pull on the valve lever trying to move it further to the closed position. It should be pushed to the stop already if in proper adjustment. If it goes further, it wasn't fully closed, you need to adjust the cable. To do that, remove the clip holding the plastic cable housing to the valve. Pull the housing toward the valve lever and reattach the clip. Now the lever will go further when set to full cold.

Thanks for the instructions. Apparently someone has removed the cable and rod that go from the control lever on the dash to the bottom of the heater box, that rod is gone too. I located the cable and rod that operate the valve in the engine compartment and moved it to the cool position. At least it's not blowing hot air until I get the missing parts. I can adjust the heat from under the hood if needed.