You probably have a bad ground connection somewhere under the dashboard. There are two places that the ground attaches one on the left & one on the right. Both are about 6in to 1 ft from the edge of the edge of the doors. I just replaced a wiring harness in a truck & it was a pain in the #*&$. It's a chore, no doubt but if it's driving you nuts then I would try that first. Good luck, John jlindsey@puppynuts.com
It is doing a guage check. Most big trucks and diesels do it. Not seen it in a gasoline engine though.
Are you talking about the digital speedometer or the whole dashboard? .
On the dashboard...
Remove the dashboard cover. Remove the retaining ring, from the speedometer. Remove the speedometer cable from the back of the speedometer. Reverse the process to install the new speedometer.
On the Dashboard Under Your Speedometer
Front and center in the dashboard...
Dashboard area where guages, speedometer, & lights are located
speedometer
Either the Speedometer itself is bad or the speedometer cable is. either one isn't too difficult if you have pulled a dashboard out before.
You can't you have to replace the whole dashboard instrument cluster assy.
I need to know also. My dashboard instrument cluster lights are out and can't see the speedometer.
You can try to knock on the dashboard area around the speedometer. Or you could resolder the PCB on the backside of your speedo. A very common problem on 406's You can try to knock on the dashboard area around the speedometer. Or you could resolder the PCB on the backside of your speedo. A very common problem on 406's