Arm Rest Heat Problem

I have been getting heat from the area of my armrest that I cannot shut off or control in the summer time. I checked the transmission and the heat is not coming from there. There is a thermostat and fan for the heat/AC for the rear seats that is attached to the armrest. If I turn the fan on in the rear armrest, the heat is pulled to the back. If I put the AC on, there is no heat at all.

What can this be? Is it the thermostat in the armrest that has malfunctioned?

Please Help!

There is a valve that controls the flow through the rear heater core if it is set to cold and the just after the truck gets to op temp then there should be no heat in the lines.
If this is the case then there is a good chance that the floorboard under the console is broken, yes I did say floorboard.
The area under the center console is a high stress point and wheelin takes its toll on 4Runners here.
Quick check: crawl under with a STRONG light and look above the transfer case, look for cracks parallel to the seat reinforcement.
Heat from the engine when moving and the cat when stopped will make its way into the console this way.
Repost with what you find, I am curious.

There is a valve that controls the flow through the rear heater core if it is set to cold and the just after the truck gets to op temp then there should be no heat in the lines.
If this is the case then there is a good chance that the floorboard under the console is broken, yes I did say floorboard.
The area under the center console is a high stress point and wheelin takes its toll on 4Runners here.
Quick check: crawl under with a STRONG light and look above the transfer case, look for cracks parallel to the seat reinforcement.
Heat from the engine when moving and the cat when stopped will make its way into the console this way.
Repost with what you find, I am curious.

I will check the area, but if this is the case, what can be done to correct the problem? And, if this is not the problem, what else could cause it?

Thanks!

Reinforcement. I wanted to cover it with two steel plates one on top and one on the bottom then bolt these together with ample amounts of RTV to seal it all up. BUT.......
Because of all the curves and interferences I was only able to put two straps down on top and huge washer on the bottom.
I may have to revisit this fix this summer as I think it's back.