LS Swap - Neutral Safety Switch input source
Thread Starter
Burning Brakes
Joined: Apr 2017
Posts: 877
Likes: 80
From: Frederick MD
LS Swap - Neutral Safety Switch input source
Good Afternoon All,
I am working on the harness for the 2002 LS1 / 4L60E I am putting in my '75. I have everything done except the neutral safety switch signal to the ECM. I know this should be grounded in neutral and park, and otherwise open, and I know how to wire up a relay to get that signal correctly from a good source, my question is what is that source? I have the new correct switch on my shifter from shiftworks and my first thought was that I can get the 12 volts from the downstream side of the switch, but it seems that the only time that 12 volts passes through the switch is when the ignition is in start, otherwise there is no voltage on either side of this switch, correct? Meaning that the ignition switch is upstream in the circuit. If this is the case how are people getting the correct signal to the ECM in park and neutral?
Thanks,
Scott
I am working on the harness for the 2002 LS1 / 4L60E I am putting in my '75. I have everything done except the neutral safety switch signal to the ECM. I know this should be grounded in neutral and park, and otherwise open, and I know how to wire up a relay to get that signal correctly from a good source, my question is what is that source? I have the new correct switch on my shifter from shiftworks and my first thought was that I can get the 12 volts from the downstream side of the switch, but it seems that the only time that 12 volts passes through the switch is when the ignition is in start, otherwise there is no voltage on either side of this switch, correct? Meaning that the ignition switch is upstream in the circuit. If this is the case how are people getting the correct signal to the ECM in park and neutral?
Thanks,
Scott
Melting Slicks
Joined: Sep 2010
Posts: 3,269
Likes: 687
On my C3 LS swap I used the Shift Works detent conversion and used the stock C3 shifter neutral safety switch. The ECM typically doesn't need a signal from the neutral safety switch. As I recall on my 71 C3 there was a purple? wire coming from the under dash wiring to the switch and the other purple wire going out to the starter.
I used a meter to check the neutral safety switch adjustment before I got the car running.. Should be open in park and neutral. And then before I put the console on and had the car running I carefully checked the park and neutral positions with the rear wheels off the ground.
On my LS swaps I have not used the "stock" 4L60E neutral safety switch on the side of the trans. but if you do per the LS1tech guys that switch will not handle the amps and it needs to feed the starter thru a relay.
I used a meter to check the neutral safety switch adjustment before I got the car running.. Should be open in park and neutral. And then before I put the console on and had the car running I carefully checked the park and neutral positions with the rear wheels off the ground.
On my LS swaps I have not used the "stock" 4L60E neutral safety switch on the side of the trans. but if you do per the LS1tech guys that switch will not handle the amps and it needs to feed the starter thru a relay.
Thread Starter
Burning Brakes
Joined: Apr 2017
Posts: 877
Likes: 80
From: Frederick MD
On my C3 LS swap I used the Shift Works detent conversion and used the stock C3 shifter neutral safety switch. The ECM typically doesn't need a signal from the neutral safety switch. As I recall on my 71 C3 there was a purple? wire coming from the under dash wiring to the switch and the other purple wire going out to the starter.
I used a meter to check the neutral safety switch adjustment before I got the car running.. Should be open in park and neutral. And then before I put the console on and had the car running I carefully checked the park and neutral positions with the rear wheels off the ground.
On my LS swaps I have not used the "stock" 4L60E neutral safety switch on the side of the trans. but if you do per the LS1tech guys that switch will not handle the amps and it needs to feed the starter thru a relay.
I used a meter to check the neutral safety switch adjustment before I got the car running.. Should be open in park and neutral. And then before I put the console on and had the car running I carefully checked the park and neutral positions with the rear wheels off the ground.
On my LS swaps I have not used the "stock" 4L60E neutral safety switch on the side of the trans. but if you do per the LS1tech guys that switch will not handle the amps and it needs to feed the starter thru a relay.
Melting Slicks
Joined: Sep 2010
Posts: 3,269
Likes: 687
Having said above you do need a brake light switch with two sets of contacts. One set for the brake lights and one set for the torque converter lock/unlock. The one I'm using on my 1980 Camaro LS swap is NAPA part number SL186. I've also used a 2002 Camaro auto brake light switch. In regards to C3's I wonder if the 1980-1982 brake light switch has two sets of contacts? If it does it might bolt right in so to speak.
Thread Starter
Burning Brakes
Joined: Apr 2017
Posts: 877
Likes: 80
From: Frederick MD
Having said above you do need a brake light switch with two sets of contacts. One set for the brake lights and one set for the torque converter lock/unlock. The one I'm using on my 1980 Camaro LS swap is NAPA part number SL186. I've also used a 2002 Camaro auto brake light switch. In regards to C3's I wonder if the 1980-1982 brake light switch has two sets of contacts? If it does it might bolt right in so to speak.
Scott
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To your original question on the neutral safety switch, ground one side of the switch and run the other side to the ecm. Don’t make it more complicated than necessary.
Thread Starter
Burning Brakes
Joined: Apr 2017
Posts: 877
Likes: 80
From: Frederick MD
Scott
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It'll work fine without it. I've run cars without the brake pedal switch for lots of miles too and have yet to have anything odd or bad happen. The TCC still works just like any other vehicle with the switch.