Engine Hourmeter connection

[nnyerges]

The hourmeter or hour counter (HM), is for counting the time that an engine is running. Some people, connects the HM to the engine power switch, but it doesn’t ensure that your engine is running. Some people, connects the HM to the engines alternator, but, alternator can fail. So where you really connect the HM to ensure that you are really counting the time that the engine is running?

 

[nnyerges]

I just answered myself: With the oil pressure switch. Thanks anyway

 

[Alpha22]

Use a relay and connect it to the oil pressure light.

Though if my alternator fails, the least of my worries would be a few hours off the hour meter.

 

[VicS]

If you connect it to the alternator output it will run all the while the battery isolator switch is closed.

If you connect to the "ignition" switch it will only run while that is on. You dont normally leave that on when the engine is not running. In most cases there would be an alarm sounding if you did .

A relay might not be needed to connect to the oil warning light.

Modern engines with computerised engine management and control systems may need more consideration.

 

[nnyerges]

For old engines, oil warning light its the answer. Modern Diesel motors have ECU where you can get all the information

 

[nnyerges]

Also you can connect it to the fuel pressure switch (positive feed), so you dont need a relay like in the oil pressure switch case