2002 Odyssey rear heat problems

I have read some other post with people having problems with their rear air/heat, but mine seems to be a little different. The front hvac works fine all the time. All the controls seem to work, etc. The rear a/c works great, blows ice cold air that you can hang meat in. The problem is that when you turn the temperature selector to get hot air to the rear, you can hear the blower running, but nothing comes out. It does not matter if you use the front controller or the rear controller to turn it to hot air, it does the same thing. Anyone with the same issue able to resolve this. Can someone tell me where to find the rear hvac air mix controller so maybe I can try to diagnose it myself. Thanks for any help you can give.