New head unit no speedo???

[NISMOPOWERED]

I have a 96 C36 and I put in an Alpine CDA7893 and now the speedo is in op! I pluged the factory unit back in and the speedo works. Is there a way around this? It does have the factory Bose system.
Thanks

[stox]

My guess, the Alpine is shorting out the speed signal sent to the HU. Disconnect that line, and that should do the trick.

[NISMOPOWERED]

Any idea what wire that is?
Thanks

[stox]

Pin 1 on the A (ie lower) connector, if I am not mistaken. I think this is also referred to as the VSS signal.