'91 240sx speedometer problems

[cimquito]

Hey guys, I've visited this forum a lot for some great information about 240's. I had the same problem as another user that posted the capacitor fix. I tried it and it worked for a while, but my soldering capabilities are mediocre at best. So I bought an off the shelf replacement for the speedometer assembly. Well I installed it last night and i turned the key to make sure it was working and sure enough it lit up and displayed 0. I was very happy. Well I drive to work this morning, it lights up like yesterday, but it still shows 0. It isn't actually displaying my speed. This is a nice shiny new unit so I am wary to blame the part. I plugged everything in as it should be. I didn't have this problem before so I don't know how it can just develop now. If anyone has any advice or solutions I would be more than appreciative. Thanks.