How to get 12 volt only when the engine is running

[trashpad]

Hello All,

I would like to install a pump and have it automatically energize when the engine is running. I have a Nanni N3.21 diesel. Any thoughts?

Kurt

[a64pilot]

connect directly to the alternator, or maybe ignition?
Do you have a bilge blower? Often they are wired connected to the ignition.

[Ex-Calif]

How much power does the pump need? Do you have an ignition key?

- wire to ignition key circuit
- Wire to the tach output of the alternator if low power
- wire a relay to the tach output that closes a higher power circuit for the pump

If you ever need to run this pump with the engine off consider a bilge pump type switch in the circuit (auto-off-manual)

[Lancerbye]

Add an oil pressure switch and control the power to your circuit with it. That way you won't drain your battery if the ignition is left on and the engine is not running.

[model 10]

You might need to use both an oil pressure switch and a relay. The contacts inside the psi switch are not meant for much of a load but plenty of small inexpensive relays will, like an automotive horn relay for example.

[Terra Nova]

Originally Posted by Guy

You might need to use both an oil pressure switch and a relay. The contacts inside the psi switch are not meant for much of a load but plenty of small inexpensive relays will, like an automotive horn relay for example.

This is the way. Or belt driven pump.

[trashpad]

That is a great plan to use a oil sending unit and a relay. Off to the auto part store.


Kurt

[a64pilot]

You may already have an oil pressure switch for your Hobbs meter
Your engine doesn't have a buzzer for when the ignition is on, but the engine isn't running? do you have an oil pressure gauge and temp gauge instead?