gpr

iTrader: (6)

I'm to the point of hooking up the last few items before i start the motor. I'm working on a 1971 chevelle and installed a 2003 5.3 motor. I stripped down the wire harness and built a fuseblock/relays as according to lt1swaps.com.

I just need to install battery cables, and the hot and switch wires from the fuse block. question

1. do you guys remove the old oem alternator wire out of the under hood wire harness? where does it go? I'd assume i no longer need it since there is a wire in the ls harness that goes to the ls alternator. Which leads me to my next question, how does the pcm control the alternator? does it sense voltage in the engine harness, then the pcm sends voltage to engage the alternator???

2. Where is a good place on a chevelle to get a switch 12 volt source? Is there a good place to splice wires? Do you simply pull power out of the fuse block under the dash? How much voltage does it require to run the pcm, engine harness, and relays?

76larkman

you can use the wire that activated old altenator for switched 12v source if want to. Thats what I did as it was on off with key rather than run another wire. Did you hook a heavy wire up to altenator stud on back to positive battery so it would charge? Or you can go from altenator to starter battery post so it charge as well hiding a wire better.

gpr

iTrader: (6)

Oh that would be great if i can use the old alternator wire for a switch power wire. Kills two birds with one stone. Just to clarify are you talking about the wire that comes from the terminal on the alternator, or the one that plugs into it and turns it on?

It looks like the old battery cables from the 350 will work. It had one big (maybe 6awg) that goes down to starter. Then had a smaller wire (10 awg) that goes to the alternator terminal for charger. It looks like these will will all fit, so i was going to reuse them.

thanks for the help!!!!

76larkman

ya the one wire in the connector is on/off 12v key source, should work ok for you as did mine. you just got to have post on back altenator going to battery somehow. Your chevelle still have a seperate regulator in system or internal regulated altenator?

gpr

iTrader: (6)

Not sure. I will be using the stock 2003 truck alternator that came on the 5.3 engine. I was assuming the pcm would detect voltage of the system (most likely from the power supplied to it), then would determine when to turn on the alternator?

This has got me thinking, does the chevelle have a voltage regulator? How does it get power for the rest of the car? From the battery terminal there is a wire coming off going to a terminal on the radiator support. I’m guessing that is what powers the rest of the system and there is a voltage regulator tied into it? I’m not really that familiar with these old cars electrical system.

76larkman

it has a regulator it probably a box on radiator support between radiator and fender on driver side. you should be ok on charging with pcm hooked up to altenator, then back post to battery. when pcm kicks it on it charges the battery from that back stud. your eliminating the car side of things so you"ll be ok. the only thing is your charging idiot light mite be on but car will be charging. I believe its hooked up at the external regulator. see what going on when getting it running. I would run some good guages anyways.

gpr

iTrader: (6)

Thank you for all your help!

Doing a little reading and testing last night. Is the voltage regulator only function to control the alternator by energizing it when the key is on? Then also regulating the voltage produce by the alternator? If so I could likely get rid of the regulator now that I am using an LS alternator that has a regulator, correct?

There are 4 wires going into the regulator and a capacitor coming off of it. A blue and white wire come from regulator and go to the alternator connector. The other two one is hot all the time (and is connected to the charging terminal of the alternator), and the other one is a keyed 12volt source. If i can remove the regulator I was thinking about using the constant 12volt and keyed 12volt for the inputs I need for the LS wire harness.

Reason I want to do that is the regulator isn't needed with the new alternator, and also the blue and wire wire for the alternator connector which was mentioned above to use as the keyed 12volt source for LS harness only has 9.5 volts coming from the regulator. Thus I think the regulator is bad, and there is no since in replacing it if it really isn't needed.

Does that make sense, and would that work?

76larkman

I dont see why you couldnt use the wire for on/off keyed 12v source. I think 1 of the non power goes to idiot dash light if not mistaken. Just use a inline fusable link so something were to happen it would only blow a fuse. You dont need the regulator anymore as the altenator plug is connected to regulator which is controlled from pcm. As long you got all altenator hooked up your car charge fine. I had a 64 nova I converted along time ago to internal regulated altenator. I remember connecting 2 wires on external regulaor(which your removing) together for it to charge using 80"s altenator I had.

sowbelle

I put a 1998 LS1 in my 71 Chevelle. I used the wire that went to the ignition coil for keyed 12v power and the old large purple start wire goes to a starter relay.
Make sure your keyed 12v source stays hot even when the key is in the start mode. My alternator setup is different than yours so I cannot help you there, but you will not need the old regulator at all. Idiot light will not work as it will have no power to it. It get turned on by keyed power and no alt power.
Checkout LT1swap.com for more wiring help

gpr

iTrader: (6)

Thats a good point. I will have to verify the keyed power source is hot in the start position. Then last thing I need to do is run power wire back to the fuel pump and I'm ready to fire it up.

Once i get it running and driving I'm going to remove all these wires I no longer need, like the alternator wires, distributor wires etc... Clean the harness up a bit.

One last question, how do you remove the engine wire harness plug from the firewall?

76larkman

there is a bolt in the middle. 3/8 socket probably as that was size on my 76 skylark. You shouldnt have to many wires. If like my skylark the big heavy wire feeding off stud back altenater is tied into wire pickup on battery post at starter. It also feeds power to heater assembly. Good luck with everything.