Mine has 2 cables. First one goes from the control slider down to the bottom of the console, passenger side, near the floor. It pushes a lever that works an air damper. The other cable goes from there thru the firewall to the heater valve. The heater valve is on the heater hose, against the firewall, kinda under the fuel filter.

Have someone work the slider control, while you watch for the cable to move at both of those places.

Air bubbles in the heater core can make it blow cold. You gotta find out whether that's your problem, or the cable.