hot wire after engine start

I need to find a wire (that would normally be found as a standard wire on almost any vehicle) that does NOT become active until AFTER the engine starts, and then remains active the entire time the engine is running.

(I've already thought of the oil pressure switch output wire and/or oil pressure idiot light).


Does anyone have any other possibilities/suggestions for a wire with the characteristics I'm looking for?

Thanks!



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The Badger

i've seen this question asked many times.. if i remember there is a remote start company whos remote starts need to see 12volts if the car has started.. i have recommended in this case to modify this curcuit so that it gives 12volts to the wire u need when the voltage is around 14(like making your own voltage check)

https://www.s10forum.com/forum/showthread.php?t=111646

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Driving a Bagged, Caddied 02 s10

There is a wire at the alternator that shows 12v when the engine is running. With the key off it shows 0v. With the key on and engine off it usually shows 0v, but it may show up to 4v....but never 12v. I use this wire on Toyota's when installing Compustar remote starters because it works better than tach sensing.

What kind of car, and what do you need the wire for?

how about using a time delay relay?

just a thought.

Guys,
Thanks for all the input on this topic.
OK, here's what I'm doing:

I'm using a heating/cooling thermostat to feed my 2nd channel input wire (it's a negative input)to remote start a vehicle.

The circuit works fine and it does remote start. The problem is, the thermostat maintains contact until the temperature reaches the setting of the thermostat.

Because of the way the R/S work internally, I MUST be able to INITIATE the remote start from the thermostat which feeds the 2nd channel negative input wire, then I MUST be able to break/open that wire (after the engine is running) for the duration of the runtime cycle.

The reason the input wire must open up is because of the way the R/S functions internally. If the input wire is not disconnected, the engine will be shut down in about 45 seconds, then will re-start and run for another 45 seconds, etc. etc.

I can build a circuit using 3 relays to resolve this, but I was looking for a simpler solution. A wire that becomes hot (or grounded) only AFTER ENGINE START/RUN would be perfect.

Thanks again for the suggestions.



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The Badger

Any particular reason you don't want to use the oil pressure switch signal to do what you want?

Guys,
Thanks for all the help on this.
I ended up using the terminal on the alternator that puts out 14V after engine startup.

Thanks JWorm !!!

I fused this wire then ran thru a dash-mounted switch to feed the coil of a relay to open/break the feed to the thermostat and a reversing polarity relay for the 2nd channel negative input wire on the remote start.

RESULT:
Heating / Cooling controlled auto-start system.
Based upon temperature setting of the thermostat, engine will start, run for preset runtime, shut down, and either remain off until the temperature calls for heating or colling again, or restart for another cycle if more heating cooling is needed.

Of course therre are many safety features involved in using this type of system.

Thans again for the help guys!



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The Badger