LS swap question
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Melting Slicks
Joined: Sep 2010
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LS swap question
I'm putting the dash back together and have a question about 12 volt full time power to the ECM. Can I use the 12 volt connection from the clock or connect the wire to the stud on the starter? Clock has been replace by aftermarket gauge. Switched 12 volt I'm planning on using the stock coil wire after I've removed the resistor wire part.
Safety Car
Joined: May 2004
Posts: 4,347
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From: los altos hills california
My 69 has two spare spade connectors labelled IGN and BAT on the fuze block. Very easy hookup, guessing yours would be the same.
Last edited by ignatz; Apr 21, 2015 at 01:47 PM. Reason: fuze
Burning Brakes
Joined: Oct 2008
Posts: 1,037
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From: Mobile Alabama
I guess it depends on a number of things, like where you mount the ECM and how your wiring harness is set up.
Here is how I would look at it - the constant 12v to the ECM does not use a lot of power, but if you tie into some other circuit, the engine will quit if that fuse pops. I would have a separate circuit (with fuse) to run the ECM. Like mentioned above.
One more point is that the Ignition ON power to the ECM must be hot with key in both CRANK and ON/RUN. Make sure your source for this power is hot in both, the original ignition is not hot in CRANK. It had a second wire coming back from the starter to the coil to provide power in CRANK. Good Luck
Here is how I would look at it - the constant 12v to the ECM does not use a lot of power, but if you tie into some other circuit, the engine will quit if that fuse pops. I would have a separate circuit (with fuse) to run the ECM. Like mentioned above.
One more point is that the Ignition ON power to the ECM must be hot with key in both CRANK and ON/RUN. Make sure your source for this power is hot in both, the original ignition is not hot in CRANK. It had a second wire coming back from the starter to the coil to provide power in CRANK. Good Luck
Melting Slicks
Joined: Feb 2009
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From: Dallas Georgia
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I guess it depends on a number of things, like where you mount the ECM and how your wiring harness is set up.
Here is how I would look at it - the constant 12v to the ECM does not use a lot of power, but if you tie into some other circuit, the engine will quit if that fuse pops. I would have a separate circuit (with fuse) to run the ECM. Like mentioned above.
One more point is that the Ignition ON power to the ECM must be hot with key in both CRANK and ON/RUN. Make sure your source for this power is hot in both, the original ignition is not hot in CRANK. It had a second wire coming back from the starter to the coil to provide power in CRANK. Good Luck
Here is how I would look at it - the constant 12v to the ECM does not use a lot of power, but if you tie into some other circuit, the engine will quit if that fuse pops. I would have a separate circuit (with fuse) to run the ECM. Like mentioned above.
One more point is that the Ignition ON power to the ECM must be hot with key in both CRANK and ON/RUN. Make sure your source for this power is hot in both, the original ignition is not hot in CRANK. It had a second wire coming back from the starter to the coil to provide power in CRANK. Good Luck
A relay and a bit of extra wiring seems to have solve my problem, but wasn't fun for a while.
Thread Starter
Melting Slicks
Joined: Sep 2010
Posts: 3,255
Likes: 687
Thanks for the help guys.
I will check out the fuse block. On previous swaps I used a new Painless universal chassis harness so it had 12 volt hot in crank and run dedicated wire.
On my BMW LS swap I had the same issue with blowing a fuse under full throttle. I added a relay with the relay power source the 12 volt stud next to the fuse box and it's worked like a champ ever since.
Thanks again.
I will check out the fuse block. On previous swaps I used a new Painless universal chassis harness so it had 12 volt hot in crank and run dedicated wire.
On my BMW LS swap I had the same issue with blowing a fuse under full throttle. I added a relay with the relay power source the 12 volt stud next to the fuse box and it's worked like a champ ever since.
Thanks again.
