My 2011 Armada had a similar issue. I followed the instructions in this video and I now have heat.
Another video I found:
This comment is what worked for me too:
"I would find a spacer that would butt up against the cover and keep pressure on that gear. stacking small washers would work as a shim as well."
Another video I found:
"I would find a spacer that would butt up against the cover and keep pressure on that gear. stacking small washers would work as a shim as well."
