Electric Speedo Question

I finally installed my Electric Speedo and took it for a test drive. And don't know what the problem is but it reads around 10 to 15 MPH to slow. I don't think I am losing my mind but it seems when I'm going 40 MPH it is showing around 29 MPH. ??

It is the Auto Meter MCX series gauges. I doubled checked the sensor wiring and I have white to the speedo and black to ground.

Can or how do you adjust a electric speedo?? The factory speedo read correctly.

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Author: admin