There is an easy fix for the never ending heat coming out of the lower
vents all summer long.

A manual coolant shut off valve located under the heater cover in front
of the shift lever works the best, and is easy to install.

The stock valve is failure prone, and even though it's shut off it still
will leak hot coolant into the front heater core.
If you look into the stock valve there is a slice cut into it to always
allow some coolant to squeak by it even though it's closed tight.

If you want no heat in the footwell a manual shut off valve is a
necessity.