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C. LIM (red) – The C.LIM or Current Limit LED should NEVER come on. This diagnostic light is used to determine the condition of the treadbelt and deck. The SCR board has a
SPD (yellow) – The SPD LED flashes on and off (relative to speed) when the speed sensor is operating properly.
GRD (red) – The GRD LED should NEVER come on. It illuminates only when the elevation potentiometer becomes out of calibration.
SERIAL (red) – The SERIAL LED should NEVER come on. It illuminates only when there is a serial error. This could be a loose or pushed pin on the main wire harness.
+5V (green) – The +5V light comes on when there is power going to the Upper Display. If the light is not on check wire harness for connections. If it ‘s not the wire harness then the MCB is defective.