Altenator to trigger relay

[iruvyouskyrine]

Hey all,

I am running an Astra power steering pump in my S15. The engine in the S15 is an RB20DET.

For the astra pumpt to run in needs +12v and earth (obviosuly), and then +12v on the sense line to turn it on. Normally you would just run the sense line to switched ignition. But then the PS pump is active when you are trying to start the car. I would like the pump not to run while the starter is cranking so that it has full power to kick the engine over (only running a small battery). 

Is there a way that i can tap into the alternator wiring and give the power steering sense line +12v when the altenator has taken over the battery and is providing sufficient power? That way the alt is powering the pump not the battery.

From what i understand the large lug on the back of the altenator is obviosuly the main +12v supply to charge the battery. There is one plug with 2 pins on the altenator and 1 pin is from the body harness that is feed back in to the altenator voltage regulator circuit so the alt knows how much voltage it is putting out, and the other goes to the dash light for the altenator. 

With the dash light one side of the light has +12v on it already from the battery to illuminate it when the altenator is not outputting, and the other side runs into one of the pins on the altenator and when it is not running (or while the car is cranking and it might only be putting out a couple of volts instead of the ~14V its supposed to) the potential differance across the bulb is enough to illuminate it. But once the altenator is up and running it is feeling +12v on both sides of the bulb, causing the bulb to extuingish?

So i could tap into the bulb wiring from the altenator but the issue is that it will still be feeling the +12V from the battery correct? 

Is there any way it's possible to do what i am asking? A google search doesnt bring up anything helpful at all. Any help is appreciated, cheers.

Josh

[GTSBoy]

Just feed the ign+ that you didn't want to run it from through a relay that is pulled open by the starter signal.  The relay will sit on the NC contacts any time you're not cranking and will not run the pump while you do crank.  All that other wizardry will only lead to pain.  Which is the path to the dark side.