I am having this issue on an 8203 AgChem Terragator with a New Leader G4 box.  There was a Greenstar Rate Controller installed and setup to run the belt and the spinner with the 2630 display.  This worked great for about a month but we began to see erratic readings from the spinner speed sensor on the display.  So it goes like this:  when we turn the spinner on at low idle they will read at 350 rpm at the spinner(with a tachometer reading) and on the 2630 in the GRC run page.  The second you give the TerraGator gas, the spinner reading will drop off to zero or below 100, and not return to 350.  At the same time the physical spinner speed will increase to 500, 600, 700, 800 as you give it more fuel (just as it should).  Basically, whenever I increase the RPM's of the Floater, the spinner speed sensor loses all voltage and the reading drops off, even when the spinners keep running smoothly.  On the AgChem console the Voltage in the machine stays constant when the rpm's are increased, unlike the Speed Sensor reading.  There is some kind of surge or wiring issue that is causing this.  This is a longshot but if anybody has any information on what I can do or check to help this straighten out any help is appreciated.  Thank you