2000 speedo goes crazy

[stang2011]

i have a stock 2000 rousch mustang 5 speed v6 100% stock with 56k miles. here is the youtube clip of the problem, this was sitting in neutral in the driveway.youtube link the speedometer goes crazy for for a while and usually starts working after driving the car a bit. i did the built in cluster diagnostic test and it will jump around also on the lcd readout scren and with a obd2 reader it will do the same also. the car used to have some crazy lights and a huge system in it before so im wondering if that had messed the electrical up or something. ive tried the searching and looked but cant find any answers. thanks

 

[wmburns]

Check the ground behind the center console. It's shared by multiple devices including the radio. It's frequently messed up during a radio install.

Check out:
My odometer goes on and off? - Ford Mustang Forums

 

[stang2011]

where exacted is the ground at behind the center console. what am i looking for exactly ? just 1 wire ?

 

[wmburns]

Take the radio out and follow the black wire. There are several coming together at the same point.