I just noticed today after doing some work on the bird that my digital dash tach and speedo are stuck on the picture attached. The weird thing is the tach after a while started to trickle down the rpm line from being full down to now being stuck on about 1k rpm. The speedo blinks between being stuck on 100 to displaying the usual 0 with km/h on it. I just spent the day putting my heat and a/c housing back in and was wondering if jostling the cable harness around that area could of caused it? I have a tt6 with a dakota digital conversion box if that helps. Nessing around with the conversion box didn't have any effect with the situation. Any help would be greatly appreciated!

 

The indicated speed for engine and vehicle rely on voltage signals from the distributor and VSS respectively; if the return signal is shorted to voltage you will get max readings. On my Berlinetta, the wiring for the tach and speedo are separate until they hit the dash I believe, but I have had the same problem and it was a ground issue after replacing the heater core (did not clean the dash gound wire enough). Check your grounds well.