If you have a service manual cd refer to procedure 54-0254 to check the cable and sensor. PM with your email address and I can send the instructions. The oil pressure sensor has a connection near the base of the oil filter. Check to see if the connection is good, this cable goes from the sensor to the connector at the back of the cluster.

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'86 300E 5 speed
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'46 Cushman Scooter
'41 Ford 9N tractor