I just purchased new hour meters for my tractors. In another forum there is a discussion on how to wire an hour meter. One thing that was mentioned was to use an oil pressure sender to establish the ground for the meter. The direction for connecting these new meters also suggested this. The Kohler motors in my tractors like the motors in most older GT does not have oil pressure. So the normal way to connect the hour meter would have it operate with just the key on. I put together a simple circuit that will have the hour meter operating with the motor trying to start or running.
This drawing could use some improvements but hopefully it gets the idea across. It uses a DPDT relay to connect the ground to the meter using a normal open contact. To energize the relay a connection is made on the starter solenoid where the wire from the ignition switch connects. A stick path is made by connecting the other normally open contact on the relay to the battery terminal on the coil. The other part of this switch is connected to the relay coil. A diode is used to keep the ignition battery from energizing the starter solenoid. Shutting off the ignition switch allows the relay to open the ground for the hour meter & the only way to get it closed is starting the tractor.This shows the completed circuit.
This is a small circuit & I have some ideas on mounting it close to the meter. When it is fully installed I will post some more pictures.