12 Volt Wire Source Help

[1QUICK4]

I need to find a power source for an S13 that gets power when you turn the key on and doesn't lose power while the engine is cranking. I can't find anything that still gets 12 volts while it's cranking. It's for an autometer cobalt boost gauge, damn those things are touchy. Is there something by the ecu or is that constant all the time?

[clark]

i remember encountering this problem when i was into carPCs. now i think theyr'e a waste of time lol...but i learned alot from this website:

http://www.carnetix.com/surviving_crank/surviving_crank.htm

there's some other junk on mp3car.com about this.

i personally think your'e wasting your time. i have never had a problem with boost gauges or any gauges. yeah, i crank my engine, they turn off, but they come right back on. i never knew this was a problem?

i guess you can wire a lead directly from the positive terminal of your battery and connect it to a toggle switch. that would be kind of cool becasuse toggle switches are fun. it'lll make you feel like your'e in the cockpit of an airplane..."boost gauge....check".

only problem is if you ever forget to turn it off, you'll kill your battery.

[njd07]

I just ordered that boost gauge...why cant you use the 12 volt off the radio or the cig lighter.

[MELLO*SOS]

use a relay and trigger off one of the power wires going to the ECU... But it sounds like a lotta wiring work just for a boost gauge, what is wrong with it turning off during cranking??

[1QUICK4]

It's not a regular boost gauge. See what happens is when u give it power it self tests, goes to -30 then back to 0 to make sure everything is zeroed out. when u crank it and u lose that power it wants to start the self test again, if it gets boost while it's doing it it throws the gauge off. hence why i need a constant ignition one. I was thinking a toggle switch but i'd rather find a different wire and not run a toggle switch, or a relay. I know there has to be a wire somewhere

[GSXRJJordan]

The FSM would have answered this for you in 30 secs. Sticking a multimeter around on your ignition terminals would have answered it for you in 2 mins.

The ignition terminal (behind where you put the key in) has all the wires you need. The wire you'll want to tap at the harness connector (I wouldn't recommend cutting it, because soldering it back together under there is a biotch) is black/white. It get's +12v through the 30A ignition fusable link when the key is on ON/START. You could use a relay setup and also tap the ACC wire (blue/white I believe) so that your boost gauge would be on during ACC/ON/START, but that's a bunch more work.

What that means is that you'll click the car to "ON", wait for the fuel pump to prime and for your boost gauge to 'self test', then start the car.

I take paypal, btw. $50/hr, and this post took 5 mins. Send $2 + 3% fees. :)

[clark]

It's not a regular boost gauge. See what happens is when u give it power it self tests, goes to -30 then back to 0 to make sure everything is zeroed out. when u crank it and u lose that power it wants to start the self test again, if it gets boost while it's doing it it throws the gauge off. hence why i need a constant ignition one. I was thinking a toggle switch but i'd rather find a different wire and not run a toggle switch, or a relay. I know there has to be a wire somewhere


why would you boost immediately after you start...do you not let your engine warm up before use?

yeah my stri gauges do a self test as well. i wouldn't even thing of even putting my car in gear until i've let it warm up for minimum 2 minutes.

maybe i'm missing something..?

[MELLO*SOS]

Probably not boost but the engine vac during cranking throws the self calibration off I guess.. We were all assuming you had a mechanical boost gauge.

GSXRJJordan gave you the best answer! I was going to suggest the ACC wire but wasn't sure if it's on during cranking?

[projectRDM]

It's called 'true' ignition, powered during key on and crank. Found at the ignition switch, can't remember color but it's the only one.