I recently followed the how to from dieselgiant about fixing the odometer on my 1980 300td. I did it and it started working perfectly. Just the other day out of no where both the speeodometer and odometer stopped working at the same time. The only thing I did to the car was a valve job recently. I took the dash apart again an disassembled the speedo unit and reassembled it and it still doesn't work. Any ideas?