[Engine] find a 12 v supply only powered when engine running

[nevajims]

Hi

I have a 2003    2.0L HDI berlingo multispace and I want to locate a fuse or voltage source which is powered up only when the engine is actually running, all the fuses in the engine compartment fuse box seem to be also powered in the igintion in half way point - either that or they are not powered in either state. 
-  anyone get an idea where I could tap into this

Jim

[GraemeT]

Off the top of my head I cannot think of any are that are not switched live on the ignition as well as work when the engine is running - somebody may have a better idea - but..

..if you cannot find one (I think there was a discussion on here awhiles back and an alternator pin out was mentioned as a possibility and maybe discounted but I cannot find the thread) consider a voltage sensing relay as used for leisure batteries? That would kick in only when the alternator is running to give a voltage > 13V - something like this?

[cancunia]

As above, a smart charge relay would be just about the closest, although IIRC, the heater fan will only run with the engine running?

[Sol]

As a side note, may be no help, but if you leave the sidelight circuit on and shut off the engine, the next time you use the vehicle, the sidelights and dash lighting do not come on, until the engine actually starts. Maybe look for something in that area if the load is not high, or use an intermediate relay to switch a heavier load once the engine is running, from the sidelights. I use mine as DRLs with LED lamps fitted.