Duel zone Auto Climate control not working

[LylePfeifer]

My 2001 Yukon XL has the automatic climate control. The front fan fails to start. This happened last December so I changed out the front control box and nothing. I then removed the resistor block, cleaned the dirt off of it and spun the fan motor. Put it back together and it worked fine until a week ago. I did the same thing and it worked for a couple of days and quit again, but it did start and run for 10 minutes on its own before quiting again. This time the back fan quit once while the front fan was still working. Now the front fan quit and the back fan still runs. The resistor block? A dead spot on the front fan motor? The temp sensor in the headliner, as it has made some noise, especially when its cold? And the dealer mention a body computer?? Any ideas out there?

Thanks, Lyle Pfeifer