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Old 09-15-2010, 03:33 PM   #1
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Default Lc-1 12V source

I just want to make sure that I can get the 12V power from this white/pink wire (located under steering column) on my fuel pump relay (pictured below). My St Sign fuse is blown, so I do not know if this 12V source will still work.
My car is a 92'.

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Is it true that if I got the 12V from my ECU, if my LC-1 shorts, it will also short my ECU?
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Old 09-15-2010, 05:35 PM   #2
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I'm not sure about the LC-1 shorting the ECU..that sounds unlikely...

I've used my ECU's 12V supply for the LC-1 for a year and half without issues. I'm pretty sure it's recommended so they have the same reference voltage.
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Old 09-15-2010, 06:49 PM   #3
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pull 12 volts directly out of the battery and simply use a relay activated by either your radio or another source my relay is hooked up to the radio. Its a miata, its only few feet of new wiring. Run it in the center console. Install the LC1 controller right in front of the shifter under the air bag key. There is a tiny spot that the LC1 controller fits perfectly in. Then lift off the rubber boot around the shifter and pass your WB sensor through there.
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Old 09-15-2010, 06:52 PM   #4
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I just used some switched 12v source from the fuse box, grounded all LC1 related grounds to the ecu ground...been working perfect
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Old 09-15-2010, 07:55 PM   #5
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Quote:
Originally Posted by gospeed81 View Post
I'm not sure about the LC-1 shorting the ECU..that sounds unlikely...

I've used my ECU's 12V supply for the LC-1 for a year and half without issues. I'm pretty sure it's recommended so they have the same reference voltage.
Actually Ken and James, the MS3 devs told me they did not like running the lc-1 off the same power line as the ECU because of the amount of amperage it can pull. I still have been running mine off there since 2007 and I don't think I have ever had a problem.
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Old 09-16-2010, 05:38 AM   #6
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I've decided to take my power off the ecu. Hope everything goes okay.
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Old 09-16-2010, 07:20 AM   #7
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I've actually moved mine from the ECU 12v supply as the LC-1 doesn't like perma-live while cranking - it can cause heater calibration errors.

I've tapped the heater core 12v supply which is huge gauge cable compared to the ECU supply. That supply also cuts during cranking, but is live with the engine running. That is what the LC-1 wants.
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Old 09-16-2010, 12:42 PM   #8
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Wow...this is all good info.

Looks like lots of options, but either a dedicated relay or that heater core wire appear to be the best. I didn't realize the LC-1 could pull a lot of amperage, but it makes sense when it's warming up.
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Old 09-16-2010, 12:53 PM   #9
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eh, 5 years on the ECU power and still going.
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Old 09-16-2010, 02:58 PM   #10
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Quote:
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eh, 5 years on the ECU power and still going.
But you have had issues with your LC-1 before. I am just saying what some smart people told me.
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Old 09-16-2010, 03:27 PM   #11
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Quote:
Originally Posted by shuiend View Post
But you have had issues with your LC-1 before. I am just saying what some smart people told me.
+1...my values did start to wander a little in spring, unexplicably.
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Old 09-16-2010, 03:29 PM   #12
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Quote:
Originally Posted by shuiend View Post
But you have had issues with your LC-1 before. I am just saying what some smart people told me.

I had to replace my sensor once. my first lc-1 had issue and was replaced under warranty.
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Old 09-16-2010, 04:17 PM   #13
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Manage your 12volts wisely. Don't want to burn traces in the ECU.
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Old 09-16-2010, 05:41 PM   #14
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If you foul the sensor you will get crazy numbers. Usually its either rich or lean with some jumps in between.
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Old 09-17-2010, 05:46 AM   #15
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Maybe we can get Joe's opinion on this. I think he is a electrical engineer?
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Old 09-17-2010, 05:59 AM   #16
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I pull my 12V from the blue diagnostic connector in the engine bay. Will I go to hell and burn?
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Old 10-07-2010, 01:36 AM   #17
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I am thinking about using a Single Pole Double Throw relay with a 12v source from the blue diagnostic connector (which is only hot when the key in the ignition is set to "on"), and ACC from the radio harness for deactivation during cranking. Right now I'm trying to figure out how to wire this.
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Can I splice the ACC wire into 85, have 86 go to radio ground, wire the 12v source to 30, and have 87a go to the LC-1?

Sorry I am really bad when it comes to wiring electronics. I am slowly learning however. I do know that the LC-1 needs close grounds to the ECU and no voltage drops.

Also some fun facts for you, the LC-1 draws 1 amp running and 2 amps during warmup. Innovate advises a minimum fuse size of 5 amps.
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Old 10-07-2010, 01:59 AM   #18
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I did some multimeter testing and found that the diagnostic connector, blower motor, and radio 12v all go to ~4-5v during cranking. The only option for LC-1 power I think is by using a relay to cut power altogether during cranking.

EDIT: forget what I said, I forgot the wiper circuit is switched during cranking. Should be easy enough to install an "add a fuse" to the wiper fuse for 12v. Easy as pie. boom. pow.

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Old 10-07-2010, 02:25 AM   #19
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The LC-1 manual states that it needs constant 12v during cranking. However, I haven't had any issues using the power window 12v and two bolts for the shifter as ground.
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Old 10-07-2010, 02:42 AM   #20
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I haven't seen any manual that states it needs a constant 12v during cranking. From what I have been gathering the low voltages (5v) messes with the lc1. However, I find it odd that innovate wouldn't compensate for this problem as this occurs in every car.

At any rate, this seems to be the ticket.
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