# RPM needle sits on Zero



## dinnie (Jul 24, 2012)

Why when I am cutting with my Mahindra 4500 is cutting, and everything is working fine, but my RPM needle on the dash window is not moving or jumping, but sits on the zero. Even after I raise my RPM handle on the steering wheel.


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## sixbales (May 18, 2011)

Hi dinnie,

I think that your tractor is too new to have the old-style cable drive system for the tachometer. Your tachometer problem could be with the tachometer itself, or with the magnetic pickup sensor, or maybe a bad connection between them. Trace the wire from the tachometer to the signal source/magnetic sensor. Some alternators are used as a signal source for the tach, while others use a magnetic sensor/pickup sensing gear teeth as they pass by.

To test the signal, use a multimeter on a sensitive AC or maybe DC scale to determine if you have a signal that varies with engine rpm. If not you can pull and clean a pickup type sensor. Post back results and we can go from there.


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