Heater problem

New owner of a 2001 4Runner Limited with 242,000 miles. The only way I can get any heat to come into the cab is by manually pushing the lever to the other side of the heater control valve located under the hood near the firewall. The cable connected to the lever is not operating. Where does that cable go to under the dash and what is it connected to. I've also noticed the air is barely warm. I suspect the heater core probably needs to be flushed.

 

Did you ever figure out the problem? I have an issue with my heater control valve, it's leaking coolant. I want to replace it but I'm not sure of the correct part number or a good after market part that works