Heat Blending Flap

[PorkandBeans]

I have what seems to be a blending flap not opening to full heat. The temp control knob will turn easily to about 80% and stop. If you turn a little harder it just stretches the cable rather than operating the flap. I can feel the flap is getting hung up on something. The problem is the flap itself is inside the heater box.

How do I access it? I have the front console, HVAC controls, glovebox trim, etc. all out but I really don't want to take the dash out (or the heater valve & core since they currently don't leak and function properly). This is my dd so I have to put it all back together today.

Thanks in advance.

[PorkandBeans]

It may also be reversed coolant lines to the heater valve as the symptoms I have are similar to this but the knob hanging at 80% red has me thinking the flap is the cause. It's clear the hoses have been off before so I may try this easier fix first. I seem to remember a thread with a photo of these hoses at the firewall but can't find it now.

[williamtii]

top hose goes to the tee and then to the thermostat. Lower hose goes to the "additional thermostat" and then to the back of the head.

[PorkandBeans]

This is how mine is set up, thanks for the confirmation. I guess I could remove this additional thermostat and see if it is faulty but then I run the risk of catastrophic valve failure and a coolant bath for my leg, as I've read happens. I think I may just live with the crappy heat, it's almost adequate when the engine is nice and warm.