"Engine Running" signal - NOT acc

[Wiregeek]

As title, looking on how to derive or make a line that comes hot when the engine is running. Almost thinking about throwing a 'digital in' pin off a microcontroller onto the tach output and software massaging to make a solid "yep, running" output signal.

The idea is to use "RUNNING" (vs. RUN) to enable a couple relays that bypass the headlight switch and turn the lights on - giving me automatic headlights. Probably end up running park/headlights/brights through a stack of 1pst relays, with the stock wiring feeding the same coils the automatic headlight circuit does, but both do it via diodes to prevent crosstalk. Planning on having the source power and all the outputs of this circuit be switched, so that if I flip a switch inside the whole assemblage just goes away, leaving only the stock controls.

Noodlin', really.

 

[Bent77]

How about more info, like what year and if the engine is original?

 

[Wiregeek]

79, original 350.

...I have no idea what ignition system I have in her. Stock, I believe.

 

[dyeager535]

I'm down to hear more about this. I wouldn't mind setting mine up with either daytime running lights, or have them come on with an optical sensor. I'm spoiled with newer vehicles.

I suppose you could use an oil pressure switch, but personally I'm not a huge fan of using something mechanical like that if it can be avoided.

It's a decent project as-is, perhaps converting to EFI would provide the ability to pull a signal via the ECM...certainly the electric fuel pump driver would do it.

 

[Wiregeek]

I'm still noodling on it. Just got the rolling-around rims, and they're baaaaaad. Gonna have to strip and paint them before I put rubber on it and can drive it more than across the yard. Priorities... An oil pressure sender feeding a start-delay relay sounds pretty plausible actually.

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Push +12 into that, low oil pressure condition = +12 output into a relay, use the relay to 'flip' the signal (so the output of the relay is +12 when good-oil-pressure).

That +12 goes into a diode bridge with the stock headlight (and park light) signal (the output of the headlight switch). The diode bridge is to keep unexpected behavior from voltage going backwards from happening. The output of that diode bridge pops _another_ relay that makes the headlights go hot. (or stock headlight relay, I don't have the wiring diagram memorized).

might run the "Engine Running" +12v through a switch, so that the driver can shut all that stuff off and just use the manual headlight controls.

 

[Truckman4life]

I would do an oil pressure switch to trigger the ground side of a relay and put the power side of the coil and also the pin 30 coming off ignition. Use a good quality switch like these from Honeywell. https://www.grainger.com/category/e...witches?brandName=HONEYWELL&filters=brandName You could easily use a relay with the normally closed circuit for the normal headlight circuit and stock wiring and then power the auto circuit off the other side of the relay(I might have worded that backwards). Might need 2 relays, one to open the regular circuit to prevent backfeeding and one to power the automatic light on function.

 

[Wiregeek]

Pretty much exactly what I'm thinking except different. I'm looking at using a couple of diodes feeding the final headlight power relay so that the stock switch and the auto light circuit won't backfeed each other. Gotta sketch out my circuit and make some notes. I think this is going on the list after fluid flush and leak repair.

 

[arcansawdave]

The oil pressure switch is definitely the way to go. GM used one from the factory to turn on the choke heater. Otherwise, the choke circuit would pull current when the key was on and the truck isn't running, possibly resulting in a no start condition as the choke would be fully released when the engine is cold. If your truck has a choke, it already has the switch. You should be able to use the existing circuit to trigger the relay. I believe they used the same switch/methodology to activate the fuel pump on TBI trucks.

 

[Wiregeek]

probably going to tee in and add a standalone. Keep my aftermarket crap separated from GM's original crap.

Just got my rims in, gotta clean 'em up and paint them before I slap some rubber on them, but also gotta get the trailer wired so I can get the boat on it but also and also and also

 

[blackhemirt]

I did this year's ago on my 67 firebird, i used the signal wire from the alternator (that goes to dash light)to trigger a relay.
U just need a diode and a relay. My setup only works if you have an external regulator though.