speedometer not working after head unit install???

[MHarvey]

Hey everyone, a buddy of mine is having a problem in his 98 Z28 with the monsoon system. He installed an aftermarket HU, just using a harness and integrating it with the factory amp for the time being. After the install was complete, the speedo in the car doesn't work any longer. He pulled the HU out, plugged the factory deck back in, and the speedo works again. I have done alot of installation work in the past and he called to ask me about it, but I've done a couple of HU installs in these cars and never heard of anything like this, can someone shed some light for me? Thanks, Mike

[Kevin]

The VSS wire in the radio harness is probably grounding out or something. Check to make sure that the wire harness adaptor is configured correctly or that the pins in it arent getting bent. VSS wire is the grren/white stripe in factory harness.

[MHarvey]

Thanks, for the information. I wasn't aware that there was even a VSS wire in the factory radio harness, but that does make sense as I believe that it was euipped with the automatic volume adjust. He's coming by tomorrow, to have me take a look at it, so I'll check to see what he's got tied in on the harness.
Thanks again
Mike