Simple question which has me a bit stumped. How can I arrange relay(s) to establish a connection when engine is running? Ie. Engine On > Connection Engine Off > No Connection I was mainly going to use this to relay my thermofan. But it could serve several purposes. I had thought of running a relay to the alternators light output. But I'm not sure this will work for two reasons. 1. Even if I disconnect everything that runs to the alternators light output. I'm not 100% sure what voltage is at this point. 2. Without disconnecting everything it comes down to this circuit having the opposite function. Ie. Engine/Alternator On > Light Off Engine/Alternator Off > Light On
*Edit* assuming you don't want it to just switch on with they key, only once the engine has started: There are probably circuits in the car you could use, but for an add on solution jaycar have switches triggered by voltage - ie higher voltage when alternator running triggers switch http://www.jaycar.com.au/productView.asp?ID=KC5377 or triggered by frequency, ie tach signal idle or higher triggers switch http://www.jaycar.com.au/productView.asp?ID=KC5378
Many, many options live in the fuse box in the engine bay. I used one of them for my thermofan relay many years ago. Or hurry up and buy nistune, use the aircon sub fan and adjust the switching point off speed and temperature like a big boy.
Yes absolutely lol, I should have said "assuming you don't want it to come on with the key, only once the engine has started"
Alright thanks guys for the last few posts. I'm sure there's many ways to do it. IGN ON & Engine Running > Connection IGN ON & Engine Not Running > No Connection If you wire it straight to ground from Ignition it will still come on either way.
So I want to hook up my driving lights so they only turn on if the engine is running? Can I Nistune for this?? No. Not unless I hack into it. You guys poke fun at me, posts get deleted whatever. But can't give me an answer???
We gave you several answers!! And IMO using Nistune and modding the Aux fan circuit is the best way for a thermofan. For an engineer you don't seem to think for yourself too hard.
That would be a matter of using the ignition ON to signal a relay that will switch on the driving lights. As soon as the engines switched off, your lights will turn off.
I think you already answered your question. Run a relay off the alternator light tied with the ignition in a logic circuit. Ignition on and alternator light on means open circuit ignition on no alternator light then closed circuit. This will be fiddly and a work around for the voltage register method mentioned from jaycar but if you are intent on ignoring the obvious choice of nistune (especially when its also the answer in other threads of yours) I think its the most straight forward option.
So what I was thinking of doing is running a Normally Closed Relay IGN >>> Solenoid >>> Alternator (Light Output) IGN >>> Switch >>> Output No, I find myself thinking a lot harder for other people.
Get the ECU to do this for you - just run another relay off the fuel pump signal - the ECU makes sure that the fuel pump only runs for a couple of seconds when the ignition is turned on, then only when the engine is running. THe FPCU modulates the voltage on the fuel pump, but it should be enough to hold a relay in at any voltage once it's pulled in. Just use a high impedance coil relay. Don't muck around with the alternator light. Not sure about Zeds, but some alternators like to see a very specific globe wattage (load), as they use the current flow through the globe to kick start the stator magnetic field on startup. Change the load significantly, and you may change the way the alternator operates, or at least its reliability. The globe actually connects the battery +ve to the alternator output. Ignition ON, engine not running so alternator output is zero = 12 volts across the globe so it glows. Start then engine and the alternator starts producing power, you have 12 volts on each side of the globe, so it goes out. You can pick an alternator that's on the way out by looking at the globe, especially at idle. If it pulses dimly or stays on dimly, then the alternator is not putting out a full 12 volts. Pulsing usually means that a diode inside the alternator has died.
OK, I was under the impression FPCU just dropped the voltage to pump if the engine is not started. But this is correct, ECU switches FPCU off if no signal is received from CAS. http://300zx.co.uk/tech/manual/manual/efec/026.gif With the alternator light, however, I'm am led to believe there are at least two possible conditions. 1. Stator based light/sense output as described above. 2. Regulator based light output which I am led to believe (may or may not depending on application) operates a normally closed relay to ground, opening connection if battery is charging. My suggestion here is based on the latter. So on one hand even though I prefer to run a voltmeter than a battery light. The fuel pump relay sounds to be a pretty good option. Thanks
Probably fine in terms of "leaving you lights on" in the car park or something. However, in terms of running a thermofan. If you simply relay directly to IGN feed it is still going to come on with key in the IGN/ACC position regardless of whether or not the engine is running. So there is nothing wrong with this. At least it would save your battery from going flat if you leave your driving/fog lights on. If you run your device from a normally open relay to fuel pump relay or normally open low pressure switch, for example. IGN fed relay and device will only be activated when the engine is running.
Ideally. But devices draining power. Ie thermofans, coming on before cranking starter motor. Are never going to help issues.
