No interior heat?

The engine temp is good right in that 80-90 tange so I'm assuming the thermostat is fine thou I do have a new just haven't swapped it out yet. Maybe when I do the motor mounts next week.

I'll take a look under the monovalve for that ball, do I just have to push it back down the housing?

Okay so I'm still working on the heat issue, I've realized that the entire heat system was bypassed. After I corrected the pipes and set it up properly I drove it for about a mile and the heat was gooing great but it also started to overheat and lost all the coolant. After getting her home I flushed all the pipes but I found that there is a majot clog where the pipe goed into the cabin through the firewall.

This must be where the coolant flows into the heater core, so is my heater core just colgged or do I need to replace it?

Also how do I get to the heater core do I have to remove the entire dash? Or could I get to it by pulling the radio and the climate control panel?

Thanks any and all advice is appreciated.