I have an 9 year old carrier weathermaker 9200 gas furnace. I'm getting no heat from the downstairs unit. The upstairs unit is working fine. I took the cover off, and I can see the black electric motor(?) spinning, yet nothing is blowing out through the vents. When I look at the bottom right front of the area below the electric motor / blower-type assembly, I see 3 LED's blinking. 3 fairly rapid flashes; followed by 1 long steady flash. It continues to do this over and over.